A1 Mathematical Operations Appendix A A-1 Exponential Arithmetic Measured quantities in this text range from very small to very large. For example, the mass of an individual hydrogen atom is 0.00000000000000000000000167 g, and the number of molecules in 18.0153 g of the substance water is 602,214,000,000,000,000,000,000. These numbers are difficult to write in conven- tional form and are even more cumbersome to handle in numerical calculations. We can greatly simplify them by expressing them in exponential form. The exponential form of a number consists of a coefficient (a number with value between 1 and 10) multiplied by a power of 10. The number is the nth power of 10. If n is a positive quantity, is greater than 1. If n is a negative quantity, is between 0 and 1. The value of Positive powers Negative powers To express the number 3170 in exponential form, we write For the number 0.00046 we write A simpler method of converting a number to exponential form that avoids intermediate steps is illustrated below. That is, to convert a number to exponential form, * Move the decimal point to obtain a coefficient with value between 1 and 10. * The exponent (power) of 10 is equal to the number of places the decimal point is moved. * If the decimal point is moved to the left, the exponent of 10 is positive. * If the decimal point is moved to the right, the exponent of 10 is negative. * 3.17 + 10 3 321 * 4.6 + 10 ,4 1234 3 1 7 0 0.0 0 0 4 6 0.00046 = 4.6 * 0.0001 = 4.6 * 10 -4 3170 = 3.17 * 1000 = 3.17 * 10 3 10 -3 = 1 10 * 10 * 10 = 1 10 3 = 0.001 10 3 = 10 * 10 * 10 = 1000 10 -2 = 1 10 * 10 = 1 10 2 = 0.01 10 2 = 10 * 10 = 100 10 -1 = 1 10 = 0.1 10 1 = 10 10 0 = 1 10 0 = 1 10 0 = 1. 10 n 10 n 10 n
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A1
MathematicalOperations
Appendix
AA-1 Exponential Arithmetic
Measured quantities in this text range from very small to very large. For example,the mass of an individual hydrogen atom is 0.00000000000000000000000167 g,and the number of molecules in 18.0153 g of the substance water is602,214,000,000,000,000,000,000. These numbers are difficult to write in conven-tional form and are even more cumbersome to handle in numerical calculations.We can greatly simplify them by expressing them in exponential form. Theexponential form of a number consists of a coefficient (a number with valuebetween 1 and 10) multiplied by a power of 10.
The number is the nth power of 10. If n is a positive quantity, is greaterthan 1. If n is a negative quantity, is between 0 and 1. The value of
Positive powers Negative powers
To express the number 3170 in exponential form, we write
For the number 0.00046 we write
A simpler method of converting a number to exponential form that avoidsintermediate steps is illustrated below.
That is, to convert a number to exponential form,
* Move the decimal point to obtain a coefficient with value between 1 and 10.
* The exponent (power) of 10 is equal to the number of places the decimalpoint is moved.
* If the decimal point is moved to the left, the exponent of 10 is positive.
* If the decimal point is moved to the right, the exponent of 10 is negative.
To convert a number from exponential form to conventional form, move thedecimal point the number of places indicated by the power of 10. That is,
Electronic calculators designed for scientific and engineering work easilyaccommodate exponential numbers. A typical procedure is to key in the num-ber, followed by the key EXP or EE. Thus, the keystrokes required for thenumber are
and the result displayed is
For the number the keystrokes are
and the result displayed is
Some calculators have a mode setting that automatically converts all num-bers and calculated results to the exponential form, regardless of the form inwhich numbers are entered. In this mode setting you can generally also set thenumber of significant figures to be carried in displayed results.
Addition and Subtraction
To add or subtract numbers written in exponential form, first express eachquantity as the same power of 10. Then add and/or subtract the coefficients asindicated. That is, treat the power of 10 as you would a unit common to theterms being added and/or subtracted. In the example that follows, convert
to and use as the common power of 10.
Multiplication
Consider the numbers and Their product is Coefficients are multiplied, and exponents are added.
Division
Consider the numbers and Their quotient is
Coefficients are divided, and the exponent of the denominator is subtracted from theexponent of the numerator.
= 2.65 * 1012-1-222= 2.65 * 104
=2.00 * 6.36 * 1.50 * 1011+2-12
14.00 * 1.802 * 10-2=
19.1 * 102
7.20 * 10-2
20.0 * 636 * 0.150
0.0400 * 1.80=
12.00 * 101216.36 * 102
211.50 * 10-12
14.00 * 10-22 * 1.80
a * 10y
b * 10z= 1a>b2 * 101y-z2
b * 10z.a * 10y
= 6.6 * 101* 10-3
= 6.6 * 10-2
= 12.20 * 4.0 * 7.52 * 101-2-3+22= 66 * 10-3
0.0220 * 0.0040 * 750 = 12.20 * 10-2214.0 * 10-3
217.5 * 1022
a * b * 101y+z2.b * 10z.a * 10y
= 4.46 * 10-2
15.60 * 10-22 + 13.8 * 10-3
2 - 11.52 * 10-22 = 15.60 + 0.38 - 1.522 * 10-2
10-20.38 * 10-23.8 * 10-3
6.25,04
-4EXP52.6
6.25 * 10-4,
6.5703
3EXP75.6
6.57 * 103
6.1 + 106* * 6,100,000
1 2 3 4 5 6
8.2 + 10,5* * 0.000082
5 4 3 2 1
6.1 0 0 0 0 0
0 0 0 0 0 8.2
The instructions given hereare for a typical electroniccalculator. The keystrokesrequired with your calculatormay be somewhat different.Look for specific instructionsin the instruction manualsupplied with the calculator.
Raising a Number to a PowerTo square the number means to determine the value orthe product According to the rule for multiplication, thisproduct is When an exponential number israised to a power, the coefficient is raised to that power and the exponent is multipliedby the power. For example,
Extracting the Root of an Exponential NumberTo extract the root of a number is the same as raising the number to a fractionalpower. This means that the square root of a number is the number to the one-half power; the cube root is the number to the one-third power; and so on. Thus,
In the following example, where the cube root is sought, the exponent is not divisible by 3; the number is rewritten with an exponent that isdivisible by 3.
A-2 LogarithmsThe common logarithm (log) of a number (N) is the exponent (x) to which thebase 10 must be raised to yield the number N. That is, means that
For simple powers of ten, for example,
Most of the numbers that result from measurements and appear in calcula-tions are not simple powers of 10, but it is not difficult to obtain logarithms ofthese numbers with an electronic calculator. To find the logarithm of a num-ber, enter the number, followed by the LOG key.
Another common example requires us to find the number having a certainlogarithm. This number is often called the antilogarithm or the inverse loga-rithm. For example, if what is N? N, the antilogarithm, is sim-ply and to find its value we enter 4.350, followed by the key Depending on the calculator used, it is usually necessary to press the key
INV or 2nd F before the log key.
If the task is to find the antilogarithm of we again note thatand The required keystrokes on a typical elec-
Some Useful RelationshipsFrom the definition of a logarithm we can write and
This means that
Similarly, it is not difficult to show that
Finally, because and
Or, in more general terms,
This expression is especially useful for extracting the roots of numbers. Thus, todetermine we write
Significant Figures in LogarithmsTo establish the number of significant figures to use in a logarithm or an-tilogarithm, use this fundamental rule: All digits to the right of the decimalpoint in a logarithm are significant. Digits to the left are used to establishthe power of 10. Thus, the logarithm is expressed to two significantfigures. The antilogarithm of should also be expressed to two signifi-cant figures; it is To help settle this point, take the antilogarithmsof and You will find these antilogs to be
and respectively. Only two significant figures arejustified.
Natural LogarithmsLogarithms can be expressed to a base other than 10. For instance, because
(read as, the logarithm of 8 to the base 2 is equal to 3 ).Similarly, Several equations in this text are derived by themethods of calculus and involve logarithms. These equations require that thelogarithm be a natural one. A natural logarithm has the base A logarithm to the base e is usually denoted as ln.
The relationship between a natural and common logarithm simplyinvolves the factor That is, for the number N,
The methods and relationships described for logarithms andantilogarithms to the base 10 all apply to the base e as well, except that therelevant keys on an electronic calculator are ln and rather than LOG
and .
A-3 Algebraic OperationsAn algebraic equation is solved when one of the quantities, the unknown, isexpressed in terms of all the other quantities in the equation. This effect isachieved when the unknown is present, alone, on one side of the equation, andthe rest of the terms are on the other side. To solve an equation, a rearrange-ment of terms may be necessary. The basic principle governing these re-arrangements is quite simple. Whatever is done to one side of the equation must bedone to the other as well.
A quadratic equation has the form where a, b, and c are con-stants (a cannot be equal to 0). A number of calculations in the text require usto solve a quadratic equation. At times, quadratic equations are of the form
Such equations can be solved by extracting the square root of each side.
More likely, however, the quadratic formula will be needed.
In Example 15-13 on page 685, the following equation must be solved.
This is a quadratic equation, but before the quadratic formula can be applied,the equation must be rearranged to the standard form: Thisis accomplished in the steps that follow.
(A.1)
Now we can apply the quadratic formula.
Note that only the value of the sign was used in solving for x. If thevalue had been used, a negative value of x would have resulted. However,
for the given situation a negative value of x is meaningless.
The Method of Successive Approximations
The quadratic equation that was just solved using the quadratic formula canbe solved by an alternative method that can be extended to equations of higherorder, such as the cubic, quartic, and quintic equations often encountered insolving equilibrium problems. To illustrate the method suppose we wish to
solve expression (A.1) without recourse to the quadratic formula. We canrewrite the equation as follows
and make a guess at the value of x, which we substitute into the right hand sideof the equation to calculate a new value of x. If we guess 0.15, which is reason-able given the starting concentrations involved in Example 15-13, we calculate
We can now use this value of x to calculate a new one.
Repeating this procedure one more time, we get
One more attempt gives a value of 0.11, which is in agreement with the answerpreviously obtained. The method that we have just used is called the methodof successive approximations.
Let us now apply the method of successive approximations to the equationobtained in the Integrative Example of Chapter 15, namely
(A.2)
The approach we can take here is to guess a value of x; evaluate the expressionto see how close to zero it comes; and then adjust the value of x accordingly.Let us start with a guess of 0.40. The result is
Clearly the value of 0.40 is too large. If we now try 0.10 we obtain a value ofWe have overshot the value of x. We can now try a value of 0.25 (halfway
between our two previous guesses) and obtain 0.11. We realize now that wehave to reduce the guessed value of x slightly to get closer to zero. If we try 0.20we obtain and if we next try the value we obtain We arenow very close to our goal of finding the value of x that satisfies the expression.One final guess of 0.23 gives a value of a very satisfactory result.
An alternative approach is to rewrite expression (A.2) as
and evaluate x as the fifth root of this new expression. If we substitute a valueof on the right side, we obtain on the left side. Now by usingthis value on the right we calculate a new value of on the left. Byusing this value we obtain on the left, and finally with this last valuewe obtain in agreement with our previous procedure. Whichmethod we use is a matter of convenience, but the second method provides anew value of x whereas the first method may require more trial and error.When using the method of successive approximations, it is often a useful strat-egy to take the average of two results in order to speed up the convergence.The method of successive approximations can be very useful, but sometimes,depending how the equation is set up, the convergence to the correct answermay be slow or the process may even diverge. In such circumstances, the ex-pression can be graphed as a function of x to ascertain where the solutionsoccur. In any event, we must always make sure that any answer obtained isreasonable from a chemical or physical point of view.
Suppose the following sets of numbers are obtained for two quantities x and yby laboratory measurement.
The relationship between these sets of numbers is not difficult to establish.
Ideally, the results of experimental measurements are best expressedthrough a mathematical equation. Sometimes, however, an exact equationcannot be written, or its form is not clear from the experimental data. Thegraphing of data is very useful in such cases. In Figure A-1 the points listedabove are located on a coordinate grid in which x values are placed along thehorizontal axis (abscissa) and y values along the vertical axis (ordinate). Foreach point the x and y values are indicated in parentheses.
The data points are seen to define a straight line. A mathematical equationof a straight line has the form
Values of m, the slope of the line, and b, the intercept, can be obtained from thestraight-line graph.
When The intercept is the point where the straight line inter-sects the y-axis. The slope can be obtained from two points on the graph.
From the straight line in Figure A-1, can you establish that m = b = 2?
The technique used above to eliminate the constant b is applied to logarith-mic functions in several places in the text. For example, the expression writtenbelow is from page 516. In this expression P is a pressure, T is a Kelvin tem-perature, and A and B are constants. The equation is that of a straight line.
equation of straight line:
We can write this equation twice, for the point and the point
The difference between these equations is
A-5 Using Conversion Factors (Dimensional Analysis)
Some calculations in general chemistry require that a quantity measured inone set of units be converted to another set of units. Consider this fact.
Divide each side of the equation by 1 m.
On the left side of the equation, the numerator and denominator are identical;they cancel.
(A.3)
On the right side they are not identical, but they are equal because they dorepresent the same length. The ratio when multiplied by a length inmeters, converts that length to centimeters. The ratio is called a conversion factor.
Consider the question, how many centimeters are there in 6.22 m? Themeasured quantity is 6.22 m, and multiplying this quantity by 1 does notchange its value.
Now replace the factor 1 by its equivalent the conversion factor (A.3).Cancel the unit, m, and carry out the multiplication.
this factorconvertsm to cm
Next consider the question, how many meters are there in 576 cm? If weuse the same factor (A.3) as before, the result is nonsensical.
A-5 Using Conversion Factors (Dimensional Analysis) A9
Because of the importanceof the cancellation of units,this problem-solving methodis often called unit analysis ordimensional analysis.
*
Factor (A.3) must be rearranged to
this factorconvertscm to m
This second example emphasizes two points.
1. There are two ways to write a conversion factor in one form or its recip-rocal (inverse). Because a conversion factor is equal to 1, its value is notchanged by the inversion, but:
2. A conversion factor must be used in such a way as to produce the neces-sary cancellation of units.
Calculations based on conversion factors are always of the form
576 cm *1 m
100 cm ¯
= 5.76 m
1 m>100 cm.
* FIGURE A-2Comparison of one squarefoot and one square meterOne meter is slightly longerthan 3 ft; is somewhatlarger than 9 ft2.
1 m2
1 ft
1 m
1 m
1 f
t
(A.4)information sought = information given * conversion factor(s)
Often several conversions must be made in sequence in order to get to thedesired result. For example, if we want to know how many yards (yd) thereare in 576 cm, we find that there is no direct conversion factor avail-able. From the inside back cover of the text, however, we do find a conversionfactor for Thus, we can develop a conversion pathway, that is, a seriesof conversion factors that will take us from centimeters to yards:
cm yd
We can use the same idea of a conversion pathway to deal with the somewhatmore challenging situation faced when the units are squared (or cubed). Consid-er the question, how many square feet correspond to an area of 1.00 squaremeter given that and Here, it may be helpfulto begin by drawing a sketch or outline of the situation. Figure A-2 represents anarea of Think of it as a square with sides 1 m long. Figure A-2 also repre-sents the length 1 ft and an area of Do you see that there is somewhatmore than in
We can write expression (A.4) as follows:
to convert to convertto to
This is the same as writing
Another way to look at the problem is to convert the length 1.00 m to feet,
Our last example incorporates several ideas discussed above. Here we willexamine the situation in which the units in both the numerator and denomi-nator must be converted. Consider the question, how many meters per sec-ond correspond to a speed of 63 mph, given that
We need to convert from miles to meters in the numerator and from hoursto seconds in the denominator. We will need to use conversion factors fromelsewhere in Section A-5 in addition to the given value. Also, we must be care-ful that our conversion factors produce the correct cancellation of units.
In an alternative approach we break down the problem into three steps:(1) Convert 63 miles to a distance in meters; (2) convert 1 hour to a time in sec-onds; and (3) express the speed as a ratio of distance over time.
Step 1.
Step 2.
Step 3.
In conclusion, we have shown (1) how to make a conversion factor; (2) thata conversion factor may be inverted; (3) that a series of conversion factors maybe used to make a conversion pathway; (4) that conversion factors may beraised to powers, if necessary; and (5) that conversions of values with units inboth the numerator and the denominator (such as miles per hour or poundsper square inch) can be performed in one step or in several steps.
B-1 Velocity and AccelerationTime elapses as an object moves from one point to another. The velocity ofthe object is defined as the distance traveled per unit of time. An automobilethat travels a distance of 60.0 km in exactly one hour has a velocity of (or ).
Table B.1 contains data on the velocity of a free-falling object. For thismotion, velocity is not constant it increases with time. The falling objectspeeds up continuously. The rate of change of velocity with time is called
acceleration. Acceleration has the units of distance per unit time per unit time.With the methods of calculus, mathematical equations can be derived for thevelocity and distance traveled in a time by an object that has a con-stant acceleration
(B.1)
(B.2)
For a free-falling object, the constant acceleration, called the acceleration dueto gravity, is Equations (B.1) and (B.2) can be used to calcu-late the velocity and distance traveled by a free-falling object.
a = g = 9.8 m>s2.
d = 12 at2
u = at
1a2.1t21d21u2
16.7 m>s60.0 km>h
Appendix
TABLE B.1 Velocity and Acceleration of a Free-Falling Body
Time Elapsed, s
Total Distance, m
Velocity, m/s
Acceleration, m/s2
0 04.9
1 4.9
14.7
2 19.6
24.5
3 44.1
34.34 78.4
B-2 Force and WorkNewton s first law of motion states that an object at rest remains at rest, andthat an object in motion remains in uniform motion unless acted upon by anexternal force. The tendency for an object to remain at rest or in uniformmotion is called inertia; a force is what is required to overcome inertia. Since theapplication of a force either gives an object motion or changes its motion, the
actual effect of a force is to change the velocity of an object. Change in velocityis an acceleration, so force is what provides an object with acceleration.
Newton s second law of motion describes the force F required to produce anacceleration a in an object of mass m.
(B.3)
The basic unit of force in the SI system is the newton (N). It is the force requiredto provide a one-kilogram mass with an acceleration of one meter per secondper second.
(B.4)
The force of gravity on an object (its weight) is the product of the mass of theobject and the acceleration due to gravity, g.
(B.5)
Work is performed when a force acts through a distance.
(B.6)
The joule (J) is the amount of work associated with a force of one newton (N)acting through a distance of one meter.
(B.7)
From the definition of the newton in expression (B.4), we can also write
(B.8)
B-3 Energy
Energy is defined as the capacity to do work, but there are other useful descrip-tions of energy as well. For example, a moving object possesses a kind of energyknown as kinetic energy. We can obtain a useful equation for kinetic energy bycombining some of the other simple equations in this appendix. Thus, becausework is the product of a force and distance (equation B.6), and force is the prod-uct of a mass and acceleration (equation B.3), we can write
(B.9)
Now, if we substitute equation (B.2) relating acceleration distance andtime into equation (B.9), we obtain
(B.10)
Finally, let s substitute expression (B.1) relating acceleration and velocityinto (B.10). That is, because
(B.11)
Think of the work in (B.11) as the amount of work necessary to produce avelocity of u in an object of mass m. This amount of work is the energy thatappears in the object as kinetic energy
(B.12)
An object at rest may also have the capacity to do work by changing its po-sition. The energy it possesses, which can be transformed into actual work, iscalled potential energy. Think of potential energy as energy stored within anobject. Equations can be written for potential energy, but the exact forms ofthese equations depend on the manner in which the energy is stored.
B-4 MagnetismAttractive and repulsive forces associated with a magnet are centered atregions called poles. A magnet has a north and a south pole. If two magnets arealigned such that the north pole of one is directed toward the south pole of thesecond, an attractive force develops. If the alignment brings like poles intoproximity, either both north or both south, a repulsive force develops. Unlikepoles attract; like poles repel.
A magnetic field exists in that region surrounding a magnet in which the in-fluence of the magnet can be felt. Internal changes produced within an ironobject by a magnetic field, not produced in a field-free region, are responsiblefor the attractive force that the object experiences.
B-5 Static ElectricityAnother property with which certain objects may be endowed is electric charge.Analogous to the case of magnetism, unlike charges attract, and like charges repel(recall Figure 2-4). The unit of charge is called a coulomb, C. In Coulomb s law,stated below, a positive force between electrically charged objects is repulsive;a negative force is attractive.
(B.13)
where is the charge on object 1,
is the charge on object 2,
r is the distance between the objects, and
is a proportionality constant called the dielectric constant,whose numerical value reflects the effect that the medium sep-arating two charged objects has on the force existing betweenthem. For a vacuum,
for other media, is greater than 1(for example, for water ).
An electric field exists in that region surrounding an electrically charged ob-ject in which the influence of the electric charge is felt. If an uncharged objectis brought into the field of a charged object, the uncharged object may under-go internal changes that it would not experience in a field-free region. Thesechanges may lead to the production of electric charges in the formerly un-charged object, a phenomenon called induction (illustrated in Figure B-1).
e = 78.5e0
e010-12 C2 J-1 m-1;8.85419 *
8.85419 * 10-12
C2
N-1 m-2 =e = e0 =
e
Q2
Q1
F =Q1 Q2
4per2
***************
Metal rod
Glass rod
Gold leaf
***
***
++++
FIGURE B-1Production of electric charges by induction in a gold-leaf electroscopeThe glass rod acquires a positive electric charge by being rubbed with a silk cloth. As the rod is brought near the electroscope, a separation of charge occurs inthe electroscope. The leaves become positively chargedand repel one another. Negative charge is attracted to the spherical terminal at the end of the metal rod. If theglass rod is removed, the charges on the electroscoperedistribute themselves, and the leaves collapse. If thespherical ball is touched by an electric conductor beforethe glass rod is removed, negative charge is removedfrom the ball. The electroscope retains a net positivecharge, and the leaves remain outstretched.
The potential energy (PE) associated with the interaction of two charged objectsis given by
(B.14)
PE is equal to the work done when the distance between the two objects isdecreased from infinity to .
B-6 Current Electricity
Current electricity is a flow of electrically charged particles. In electric currents inmetallic conductors, the charged particles are electrons; in molten salts or inaqueous solutions, the particles are both negatively and positively charged ions.
As pointed out in Section B-5, the unit of electric charge is called a coulomb (C).The unit of electric current known as the ampere (A) is defined as a flow of onecoulomb per second through an electrical conductor. Two variables determinethe magnitude of the electric current I flowing through a conductor. These arethe potential difference, or voltage drop, E, along the conductor, and the electri-cal resistance of the conductor, R. The units of voltage and resistance are the volt (V) and ohm, respectively. The relationship of electric current, voltage, andresistance is given by Ohm s law.
(B.15)
One joule of energy is associated with the passage of one coulomb of elec-tric charge through a potential difference (voltage) of one volt. That is, one
volt-coulomb. Electric power refers to the rate of production (orconsumption) of electric energy. It has the unit watt (W).
Since one coulomb per second is a current of one ampere,
(B.16)
Thus, a 100-watt light bulb operating at 110 V draws a current of
B-7 Electromagnetism
The relationship between electricity and magnetism is an intimate one. Inter-actions of electric and magnetic fields result in (1) magnetic fields associatedwith the flow of electric current (as in electromagnets), (2) forces experiencedby current-carrying conductors when placed in a magnetic field (as in electricmotors), and (3) electric current being induced when an electric conductor ismoved through a magnetic field (as in electric generators). Several observa-tions described in this text can be understood in terms of electromagneticphenomena.
SI UnitsCThe system of units that will in time be used universally for expressing allmeasured quantities is Le Système International d Unités (The InternationalSystem of Units), adopted in 1960 by the Conference Générale des Poids etMeasures (General Conference of Weights and Measures). A summary of someof the provisions of the SI convention is provided here.
C-1 SI Base Units
A single unit has been established for each of the basic quantities involved inmeasurement. These are as follows:
Appendix
Physical Quantity Unit Symbol
Length Meter mMass Kilogram kgTime Second sElectric current Ampere ATemperature Kelvin KLuminous intensity Candela cdAmount of substance Mole molPlane angle Radian radSolid angle Steradian sr
C-2 SI Prefixes
Distinctive prefixes are attached to the base unit to express quantities that aremultiples (greater than) or submultiples (less than) of the base unit. The multiplesand submultiples are obtained by multiplying the base unit by powers of ten.
Multiple Prefix Symbol Submultiple Prefix Symbol
1012 tera T 10-1 deci d
109 giga G 10-2 centi c
106 mega M 10-3 milli m
103 kilo k 10-6 micro m
102 hecto h 10-9 nano n
101 deka da 10-12 pico p
10-15 femto f
10-18 atto a
C-3 Derived SI Units
A number of quantities must be derived from measured values of the SI basequantities [for example, volume has the unit ]. Two sets of derivedunits are given, those whose names follow directly from the base units and
Physical Quantity Unit Symbol In Terms of SI Units
Frequency hertz Hz s-1
Force newton N kg m s-2
Pressure pascal Pa N m-2
Energy joule J kg m2 s-2
Power watt W J s-1
Electric charge coulomb C A sElectric potential difference volt V J A-1 s-1
Electric resistance ohm Æ V A-1
Physical Quantity Unit SymbolDefinition of SI Units
Length ångstrom Å 1 * 10-10 mForce dyne dyn 1 * 10-5 NEnergy erg erg 1 * 10-7 JEnergy calorie cal 4.184 JPressure atmosphere atm 101 325 PaPressure millimeter of mercury mmHg 133.322 PaPressure torr Torr 133.322 Pa
those that are given special names. Notice that the units used in the text differin some respects from those in the table. For example, for the most part, thetext expresses density as molar mass as molar volume as
or and molar concentration (molarity) as or M.mol L-1,L mol-1,mL mol-1g mol-1,g cm-3,
C-4 Units to Be Discouraged or Abandoned
There are several commonly used units whose use is to be discouraged andultimately abandoned. Their gradual disappearance is to be expected, thougheach is used in this text. A few such units are listed.
Two other SI conventionsare illustrated through thistable: (a) Units are written insingular form meter or m,not meters or ms; (b) negativeexponents are preferred tothe shilling bar or solidus that is, and not
and In somechapters both ways ofexpressing units have beenused as you need to becomfortable with bothsystems.
m>s>s.m>sm s-2,m s-1
(>),
*
Another SI convention isimplied here. No commas are used in expressing largenumbers. Instead, spaces areleft between groupings ofthree digits, that is, 101 325rather than 101,325. Decimalpoints are written either asperiods or commas. Numbersin this text retained thecomma separators innumbers of at least fivedigits.
The electron configurations printed in red are those of the noble gases. Each noble gas configuration serves as the core of the electron configurations of the elements that follow it, until the next noble gas is reached. Thus, [He] represents the coreconfiguration of the second period elements; [Ne], the third period; [Ar], the fourth period; [Kr], the fifth period; [Xe], the sixthperiod; and [Rn], the seventh period.
TABLE D.2 Thermodynamic Properties of Substances at 298.15 K*. Substances are at 1 barpressure. For aqueous solutions, solutes are at unit activity (roughly 1 M). Data for ions inaqueous solution are relative to values of zero for and for H*S*G*f ,H*f ,
*Data for inorganic substances and for organic compounds with up to two carbon atoms per molecule are adapted from D. D. Wagman, et al., The NBS Tables of Chemical Thermodynamic Properties: Selected Values for Inorganic and and Organic Substances in SI Units Journal of Physical and Chemical Reference Data 11 (1982) Supplement 2. Data for other organiccompounds are from J. A. Dean, Lange s Handbook of Chemistry. 15th ed., McGraw-Hill, 1999, and other sources.
C2C1
Z04_PETR4521_10_SE_APP4.QXD 1/22/10 1:14 AM Page A18
D-2 Thermodynamic Properties of Substances at 298.15 K A19
aData are at various temperatures around room temperature, from 18 to .bFor a solubility equilibrium of the type .cThe ligands referred to in this table are monodentate: bidentate: ethylenediamine (en),oxalate ion (ox); tetradentate: ethylenediaminetetraacetato ion, dThe values are cumulative or overall formation constants (see page 1094).Kf
*The isotopic mass data are from G. Audi and A. H. Wapstra, and M. Dedieu, Nuclear Physics A,volume 565, pages 1-65 (1993) and G. Audi and A. H. Wapstra, Nuclear Physics A, volume 595,pages 409-480 (1995). The percent natural abundance data are from K.J.R. Rosman and P.D.P. Taylor, Pure and Applied Chemistry, volume 70, pages 217-235 (1998).
Z04_PETR4521_10_SE_APP4.QXD 1/22/10 2:35 AM Page A30
As you study chemistry by reading this book and attending class, you willencounter many ideas and concepts. The task of linking them together can bequite daunting. An effective way to accomplish this task is through conceptmapping. A concept map is a visual map presenting the relationships amonga set of connected concepts and ideas. It is a tangible way to display how yourmind perceives a particular topic. By constructing a concept map, you re-flect on what you understand and what you do not understand. In a conceptmap, each concept, usually represented by a word or two in a box, is connectedto other concept boxes by lines or arrows. A word or brief phrase adjacent tothe line or arrow defines the relationship between the connected concepts.Each major concept box has lines to and from several other concept boxes,thereby generating a network, or map.
E-1 How to Construct a Concept Map
1. To create a concept map, construct a list of facts, terms, and ideas that youthink are in any way associated with the topic, based on your reading andclass attendance. Start by asking yourself, what was the class or readingassignment about? The answer to this question will provide the initial(most general) concepts. The list of concepts will grow as you think fur-ther about the answer to this question. You can review the chapter sum-maries, which emphasize the important points of the chapters, as well asthe key terms of that chapter.
2. Review the concepts in your list, and categorize them from most general tomost specific. Keep in mind that several of the concepts may have the samelevel of generality. At other times, it may be difficult to determine the rela-tive importance of two related concepts; to get around this dilemma, tryposing the following question: Which concept can be understood withoutreference to the other? The answer is likely the more general concept.
3. Once the categories have been decided, center the most general concept atthe top of the page, and draw a box around it.
4. Arrange the next-most-general rank of concepts below the most generalconcept. Draw boxes around these concepts, and draw lines linking themto the most general concept. The links should have arrowheads to showthe directions in which they should be read.
5. The next step is to label the linkages with short phrases, or even singlewords, which properly relate the linked concepts. When you place concept 1,a linkage phrase, and concept 2 in sequence, a sensible phrase shouldresult. For example, measurements (concept 1) generate (linkage phrase)numbers (concept 2) that have (linkage phrase) uncertainty (concept 3).The inclusion of linkage labels is important. The appropriate linkagephrase shows that you understand the relationship between the concepts.
6. Proceed down the page, adding rows of ever-more-specific concepts.The most specific concepts should end up at the bottom of your map.
7. Throughout the map, search for cross-links between closely related con-cepts appearing on the same line. Use dashed lines with double arrow-heads to indicate the cross-links.
8. As a last step, assess the map and redraw it if necessary to produce a morelogical and neat map.
Once you have constructed the map, check that a concept appears only onceand that you have labeled all linkages. Finally, remember that there is no onecorrect concept map for a collection of concepts. However, some concept mapsare much more effective than others at displaying the relationships among agiven set of concepts.
The diagram in this appendix represents a concept map for the scientificmethod and measurements. Notice that the concept of SI units could be furtherconnected to such concepts as fundamental units and derived units.
GlossaryFAbsolute configuration refers to thespatial arrangement of the groupsattached to a chiral carbon atom. The two possibilities are D and L.
Accuracy is the closeness of ameasured value to the true or accepted value of a quantity.
Acetyl group (See acyl.)
An achiral molecule has a structurethat is superimposable on its mirrorimage. (See also chiral.)
An acid is (1) a hydrogen-containingcompound that can produce hydrogenions, (Arrhenius theory); (2) a protondonor (Brønsted Lowry theory); (3) anatom, ion, or molecule that can accepta pair of electrons to form a covalentbond (Lewis theory).
An acid base indicator is a substanceused to measure the pH of a solutionor to signal the equivalence point in an acid base titration. The nonionizedweak acid form has one color and the anionic form, a different color.
An acid ionization constant, is theequilibrium constant for the ionizationreaction of a weak acid.
An acid salt contains an anion that canact as an acid (proton donor); examplesare and
The actinides are a series of radioactive elements characterized by partially filled orbitals in their atoms.
An activated complex is anintermediate in a chemical reactionformed through collisions betweenenergetic molecules. Once formed, itdissociates either into the productsor back to the reactants.
Activation energy is the minimumtotal kinetic energy that moleculesmust bring to their collisions for achemical reaction to occur.
Active sites are the locations at whichcatalysis occurs, whether on thesurface of a heterogeneous catalyst or an enzyme.
Activity is the effective concentrationof a species. It is obtained as the product
5f1Z = 90 - 1032
NaH2PO4.NaHSO4
Ka ,
H+
of an activity coefficient and the ratioof the stoichiometic concentration orpressure to that of a reference state.
The actual yield is the measured
quantity of a product obtained in achemical reaction. (See also theoreticalyield and percent yield.)
The acyl group is . If this is called the formyl group;
acetyl; and benzoyl.
An addition elimination reaction isthe overall reaction that occurs whencompounds are interconverted. Itinvolves (1) a nucleophilic additionto the carbonyl carbon to form atetrahedral intermediate, followedby (2) an elimination reaction thatregenerates the carbonyl group.
In an addition reaction, a moleculeadds across a double or triple bond in another molecule.
An adduct is a compound formed byjoining together two simpler moleculesthrough a coordinate covalent bond,such as the adduct of and
pictured on page 948.
Adenosine diphosphate (ADP) andadenosine triphosphate (ATP) areagents involved in energy transfersduring metabolism. The hydrolysis ofATP produces ADP, the ion and a release of energy.
Adhesive forces are intermolecularforces between unlike molecules, suchas molecules of a liquid and of asurface with which it is in contact.
ADP (See adenosine diphosphate.)
Alcohols contain the functional groupand have the general formula
ROH.
Aldehydes have the general formula
.
Alicyclic hydrocarbon molecules havetheir carbon atom skeletons arrangedin rings and resemble aliphatic (ratherthan aromatic) hydrocarbons.
C HR
O
¬OH
HPO4
2-,
(C2H5)2OAlCl3
R = C6H5,R = CH3,
R = H,C R
O
Aliphatic hydrocarbon molecules havetheir carbon atom skeletons arrangedin straight or branched chains.
Alkali metals is the family name forthe group 1 elements of the periodictable.
Alkaline earth metals is the familyname for the group 2 elements of theperiodic table.
Alkane hydrocarbon molecules haveonly single covalent bonds betweencarbon atoms. In their chain structuresalkanes have the general formula
Alkene hydrocarbons have one ormore carbon-to-carbon double bondsin their molecules. The simple alkeneshave the general formula
Alkyl groups are alkane hydrocarbonmolecules from which one hydrogenatom has been extracted. For example,the group is the methyl group;
is the ethyl group.
Alkyne hydrocarbons have one ormore carbon-to-carbon triple bonds intheir molecules. The simple alkyneshave the general formula
An alloy is a mixture of two or moremetals. Some alloys are solid solutions,some are heterogeneous mixtures, andsome are intermetallic compounds.
An alpha ( ) particle is a combinationof two protons and two neutronsidentical to the helium ion, that is,
Alpha particles are emitted insome radioactive decay processes.
Alums are sulfates of the generalformula, M(I)M(III)M(I) is most commonly an alkali metalor ammonium ion, and M(III) is mostcommonly or
Amalgams are metal alloys containingmercury. Depending on theircompositions, some are liquid andsome are solid.
An amide is derived from theammonium salt of a carboxylic acidand has the general formula
An amine is an organic base havingthe formula (primary), (secondary), or (tertiary),depending on the number of hydrogenatoms of an molecule that arereplaced by R groups.
An -amino acid is a carboxylic acidthat has an amino group attached to the carbon atom adjacentto the carboxyl group
Amplitude is the height of the crest of awave above the center line of the wave.
Amphiprotic substances can act eitheras an acid or as a base.
Amphoteric is the term used todescribe the ability of certain oxidesand hydroxo compounds to act aseither acids or bases.
An angular wave function, isthe part of a wave function thatdepends on the angles and when theSchrüdinger wave equation is expressedin spherical polar coordinates. (See alsoradial wave function.)
Anhydride is a term meaning withoutwater. An acid anhydride is anelement oxide that reacts with waterto form an acid, and a base anhydride,to form a base.
An anion is a negatively charged ion.An anion migrates toward the anodein an electrochemical cell.
The anode is the electrode in anelectrochemical cell at which anoxidation half-reaction occurs.
In the anti conformation, the methylgroups are diagonally opposite eachother.
An antibonding molecular orbitaldescribes regions in a molecule in whichthere is a low electron probability orcharge density between two bondedatoms.
An aprotic solvent is a solvent whosemolecules do not have a hydrogen atombonded to an electronegative element.
An arenium ion is a cationic species
with structural formula .An arenium ion is formed whenan electrophile accepts anelectron pair from the system ofthe benzene ring.
Aromatic hydrocarbons are organicsubstances whose carbon atomskeletons are arranged in hexagonalrings, based on benzene,
Asymmetric is the term used todescribe a C atom with four differentsubstituent groups. A molecule withsuch a C atom is chiral.
One atmosphere (atm) is the pressureexerted by a column of mercury exactly
C6H6.
p1E+2
H
E
*
fu
Y1u, f2,
(¬COOH).
(¬NH2)A
NH3
R3NR2NHRNH2
760 mm high when the density ofmercury is 13.5951 and theacceleration due to gravity is
The atom is the basic building block ofmatter. The number of different atomscurrently known is 114. A chemicalelement consists of a single type of atom,and a chemical compound consists oftwo or more different kinds of atoms.
The atomic mass (weight) of an elementis the average of the isotopic massesweighted according to the naturallyoccurring abundances of the isotopes of the element and relative to the valueof exactly 12 u for a carbon-12 atom.
An atomic mass unit, u, is used toexpress the masses of individualatoms. One u is the mass of acarbon-12 atom.
The atomic number, Z, is the number ofprotons in the nucleus of an atom. It isalso the number of electrons outside thenucleus of an electrically neutral atom.
Atomic (line) spectra are produced bydispersing light emitted by excitedgaseous atoms. Only a discrete set ofwavelength components (seen as coloredlines) is present in a line spectrum.
ATP (See adenosine triphosphate.)
The aufbau process is a method ofwriting electron configurations. Eachelement is described as differing fromthe preceding one in terms of theorbital to which the one additionalelectron is assigned.
An average bond energy is the averageof bond-dissociation energies for anumber of different species containinga particular covalent bond. (See alsobond dissociation energy.)
The Avogadro constant, has a value of It is thenumber of elementary units in one mole.
Avogadro s law (hypothesis) states thatat a fixed temperature and pressure,the volume of a gas is directlyproportional to the amount of gas andthat equal volumes of different gases,compared under identical conditionsof temperature and pressure, containequal numbers of molecules.
An azeotrope is a solution that boils ata constant temperature, producingvapor of the same composition as theliquid. In some cases, the azeotropeboils at a lower temperature than thesolution components, in other cases, ata higher temperature.
A balanced equation has the samenumber of atoms of each type on bothsides. (See also chemical equation.)
Band theory is a form of molecularorbital theory to describe bonding inmetals and semiconductors.
6.02214 * 1023 mol-1.NA ,
1>12
g = 9.80665 m>s2.
g>cm3One bar is equal to 100 kilopascals
A barometer is a device used to measurethe pressure of the atmosphere.
Barometric pressure is the prevailingpressure of the atmosphere asindicated by a barometer.
A base is (1) a compound thatproduces hydroxide ions, inwater solution (Arrhenius theory);(2) a proton acceptor (Brønsted Lowrytheory); (3) an atom, ion, or moleculethat can donate a pair of electrons toform a covalent bond (Lewis theory).
A base ionization constant, is theequilibrium constant for the ionizationreaction of a weak base.
Basicity is a measure of the tendencyof an electron pair donor to react witha proton.
The basic oxygen process is theprincipal process used to convertimpure iron (pig iron) into steel.
A battery is a voltaic cell [or a group ofvoltaic cells connected in series ( to )]used to produce electricity fromchemical change.
bcc (See body-centered cubic.)
A benzyl group is a methyl group with one hydrogen atom replaced by a phenyl group.
A beta ( ) particle is an electronemitted as a result of the conversion of aneutron to a proton in certain atomicnuclei undergoing radioactive decay.
A bidentate ligand attaches itself tothe central atom of a complex at twopoints in the coordination sphere.
A bimolecular process is anelementary process involving thecollision of two molecules.
Binary compounds are compoundscomposed of two elements.
A body-centered cubic (bcc) crystalstructure is one in which the unit cellhas structural units at each corner andone in the center of the cube.
Boiling is a process in whichvaporization occurs throughout aliquid. It occurs when the vaporpressure of a liquid is equal tobarometric pressure.
A bomb calorimeter is a device usedto measure the heat of a combustionreaction. The quantity measured is theheat of reaction at constant volume,
A bond angle is the angle between twocovalent bonds. It is the angle betweenhypothetical lines joining the nuclei oftwo atoms to the nucleus of a third atomto which they are covalently bonded.
Bond-dissociation energy, D, is thequantity of energy required to break onemole of covalent bonds in a gaseous
species, usually expressed in (See also average bond energy.)
Bond length (bond distance) is thedistance between the centers of twoatoms joined by a covalent bond.
Bond order is one-half the differencebetween the numbers of electrons inbonding and in antibonding molecularorbitals in a covalent bond. A singlebond has a bond order of 1; a doublebond, 2; and a triple bond, 3.
A bond pair is a pair of electronsinvolved in covalent bond formation.
A bonding molecular orbital describesregions of high electron probability orcharge density in the internuclearregion between two bonded atoms.
Boyle s law states that the volume of a fixed amount of gas at a constanttemperature is inversely proportionalto the gas pressure.
In a bridged halonium ion, a halogenatom (X) is bonded to (bridges) twocarbon atoms that are bonded to each
other: . The halogen
atom has a complete octet, comprisingtwo bonding pairs and two lone pairs,and it bears a formal charge of If thehalogen atom is chlorine or bromine, the ion is called a chloronium orbromonium ion.
Buffer capacity refers to the amount ofacid and/or base that a buffer solutioncan neutralize while maintaining anessentially constant pH.
Buffer range is the range of pH valuesover which a buffer solution canmaintain a fairly constant pH.
A buffer solution resists a change inits pH. It contains components capableof neutralizing small added amountsof acids and base.
By-products are substances producedalong with the principal product in achemical process, either through themain reaction or a side reaction.
Calcination refers to the decompositionof a solid by heating at temperaturesbelow its melting point, such as thedecomposition of calcium carbonate to calcium oxide and
The calorie (cal) is the quantity of heatrequired to change the temperature ofone gram of water by one degreeCelsius.
A calorimeter is a device (of whichthere are numerous types) used tomeasure a quantity of heat.
A carbohydrate is a polyhydroxyaldehyde, a polyhydroxy ketone, aderivative of these, or a substance
CO2(g).
1+.
C C
X
*
kJ mol-1. that yields them upon hydrolysis.Carbohydrates can be viewed ashydrates of carbon, in the sense that
their general formulas are
Carbon black is a finely dividedamorphous form of carbon preparedby the incomplete combustion ofhydrocarbons.
The carbonyl group is found inaldehydes, ketones, and carboxylic
acids .
The carboxyl group is .
A carboxylic acid has one or morecarboxyl groups attached to ahydrocarbon chain or ring structure.
C OH
O
C O
Cx(H2O)y .
Charles s law states that the volume of a fixed amount of gas at a constantpressure is directly proportional to the Kelvin (absolute) temperature.
A chelate results from the attachment ofpolydentate ligands to the central atomof a complex ion. Chelates are five- orsix-membered rings that include thecentral atom and atoms of the ligands.
A chelating agent is a polydentateligand. It simultaneously attachesto two or more positions in thecoordination sphere of the centralatom of a complex ion.
Chelation is the process of chelateformation.
The chelation effect refers to anexceptional stability conferred to acomplex ion when polydentate ligandsare present.
Chemical change (See chemicalreaction.)
Chemical energy is the energyassociated with chemical bonds andintermolecular forces.
A chemical equation is a symbolicrepresentation of a chemical reaction.Symbols and formulas are used torepresent reactants and products, andstoichiometric coefficients are used tobalance the equation. (See alsobalanced equation.)
A chemical formula represents therelative numbers of atoms of each kind in a substance through symbolsand numerical subscripts.
A chemical property is the ability (or inability) of a sample of matter toundergo a particular chemical reaction.
A chemical reaction is a process inwhich one set of substances (reactants)is transformed into a new set ofsubstances (products).
Chemical symbols are abbreviations ofthe names of the elements consisting ofone or two letters (e.g., and ).
Chiral refers to a molecule with astructure that is not superimposable onits mirror image. (See also enantiomers.)
The term cis describes geometricisomers in which two groups areattached on the same side of a doublebond in an organic molecule, or alongthe same edge of a square in a square-planar complex, or at two adjacentvertices of an octahedral complex. (Seealso geometric isomerism.)
cis trans isomerism is a type ofstereoisomerism.
A closed system is one that canexchange energy but not matter with its surroundings.
Cohesive forces are intermolecularforces between like molecules, such as within a drop of liquid.
Ne = neonN = nitrogen
A catalyst provides an alternativemechanism of lower activation energyfor a chemical reaction. The reaction is speeded up, and the catalyst isregenerated.
The cathode is the electrode of anelectrochemical cell where a reductionhalf-reaction occurs.
Cathode rays are negatively chargedparticles (electrons) emitted at thenegative electrode (cathode) in thepassage of electricity through gases at very low pressures.
Cathodic protection is a method ofcorrosion control in which the metalto be protected is joined to a moreactive metal that corrodes instead. The protected metal acts as the cathode of a voltaic cell.
A cation is a positively charged ion. Acation migrates toward the cathode inan electrochemical cell.
The cell is the fundamental unit ofliving organisms.
A cell diagram is a symbolicrepresentation of an electrochemicalcell that indicates the substancesentering into the cell reaction, electrodematerials, solution concentrations, etc.
The cell voltage (potential), isthe potential difference (voltage)between the two electrodes of anelectrochemical cell.
The Celsius temperature scale is based on a value of 0 for the normalmelting point of ice and for thenormal boiling point of water.
A central atom in a structure is anatom that is bonded to two or moreother atoms.
In chain-reaction polymerization, areaction is initiated by opening up a carbon-to-carbon double bond.Monomer units add to free-radicalintermediates to produce a long-chainpolymer.
The charge density, is the chargeper unit volume in a cation.
Coke is a relatively pure form ofcarbon produced by heating coal out of contact with air (destructivedistillation).
Colligative properties vaporpressure lowering, freezing pointdepression, boiling point elevation,osmotic pressure have values thatdepend on the number of soluteparticles in a solution but not on their identity.
A colloid is a mixture that containsparticles that are larger than ionsor molecules but are stillsubmicroscopic.
The common-ion effect describes theeffect on an equilibrium by a substancethat furnishes ions that can participatein the equilibrium.
A complementary color is a secondarycolor that mixes with the oppositeprimary color on the color wheel toproduce white light in additive colormixing or black in subtractive colormixing.
A complex is a polyatomic cation,anion, or neutral molecule in whichgroups (molecules or ions) calledligands are bonded to a central metalatom or ion.
A complex ion is a complex having anet electrical charge.
Composition refers to the componentsand their relative proportions in asample of matter.
A compound is a substance made upof two or more elements. It does notchange its identity in physical changes,but it can be broken down into itsconstituent elements by chemicalchanges.
Concentration (1) refers to thecomposition of a solution. (2) Seeextractive metallurgy.
In a concentration cell identicalelectrodes are immersed in solutions ofdifferent concentrations. The voltage(emf) of the cell is a function simply of theconcentrations of the two solutions.
Condensation is the passage ofmolecules from the gaseous state tothe liquid state.
A condensed structural formula is asimplified representation of a structuralformula.
Conformations refer to the differentspatial arrangements possible in amolecule. Examples are the boatand chair forms of cyclohexane.
A conjugate acid is formed when aBrønsted Lowry base gains a proton.Every base has a conjugate acid.
A conjugate acid base pair is pair ofmolecules or ions for which the chemicalformulas differ by a single proton: H +
(e.g., and and and and ).
A conjugate base remains after aBrønsted Lowry acid has lost a proton.Every acid has a conjugate base.
Consecutive reactions are two or morereactions carried out in sequence. Aproduct of each reaction becomes areactant in a following reaction until a final product is formed.
Constitutional isomers have differentbond connectivities, and thus differentskeletal structures.
The contact process is a process for themanufacture of sulfuric acid having asits key reaction the oxidation of to in contact with a catalyst.
Control rods are neutron-absorbingmetal rods (e.g., Cd) that are used tocontrol the neutron flux in a nuclearreactor and thereby control the rate of the fission reaction.
In a coordinate covalent bond,electrons shared between two atomsare contributed by just one of theatoms. As a result, the bonded atomsexhibit formal charges.
Coordination compounds are neutralcomplexes or compounds containingcomplex ions.
Coordination number is the number ofpositions around a central atom whereligands can be attached in the formationof a complex. Applied to a crystallinesolid, coordination number signifies thenumber of nearest neighboring atoms(or ions of opposite charge) to any givenatom (or ion) in a crystal.
Coupled reactions are sets of chemicalreactions that occur together. One (ormore) of the reactions taken alone is(are) nonspontaneous and other(s),spontaneous. The overall reaction isspontaneous.
A covalent bond is formed whenelectrons are shared between a pair ofatoms. In valence bond theory, thesharing of the electrons is said tooccur in the region in which atomicorbitals overlap.
Covalent radius is one-half thedistance between the centers of twoatoms that are bonded covalently. It isthe atomic radius associated with anelement in its covalent compounds.
The critical point refers to thetemperature and pressure at which aliquid and its vapor become identical.It is the highest temperature point onthe vapor pressure curve.
Crystal field theory describes bondingin complexes in terms of electrostaticattractions between ligands and thenucleus of the central metal. Particularattention is focused on the splitting ofthe d energy level of the central metal.
SO3(g)SO2(g)
H2PO4
-NH3; H3PO4NH4
+
OH-;H2O; H2OH3O+ Cubic closest packed is one of the twoways in which spheres can be packedto minimize the amount of free spaceor voids among them.
Dalton s law of partial pressuresstates that in a mixture of gases, thetotal pressure is the sum of the partialpressures of the gases present. (Seealso partial pressure.)
The dashed and solid wedge linenotation is a method of conveying athree-dimensional perspective to astructure plotted in a plane.
The d block refers to that section of theperiodic table in which the process oforbital filling (aufbau process) involvesa d subshell.
A decay constant is a first-order rateconstant describing radioactive decay.
Degree of ionization refers to theextent to which molecules of a weakacid or weak base ionize. The degree of ionization increases as the weakelectrolyte solution is diluted. (See alsopercent ionization.)
The degree of unsaturation is equal tothe total number of bonds and ringstructures in a molecule.
Degenerate orbitals are orbitals thatare at the same energy level.
A delocalized molecular orbitaldescribes a region of high electronprobability or charge density thatextends over three or more atoms.
Denaturation refers to the loss ofbiological activity of a protein broughtabout by changes in its secondary andtertiary structures.
Density is a physical propertyobtained by dividing the mass of amaterial or object by its volume(i.e., mass per unit volume).
Deoxyribonucleic acid (DNA) is thesubstance that makes up the genes ofthe chromosomes in the nuclei of cells.
Deposition is the passage of moleculesfrom the gaseous to the solid state.
Detergents are cleansing agents thatact by emulsifying oils. Most commonamong synthetic detergents are thesalts of organic sulfonic acids,
Dextrorotatory means the ability torotate the plane of polarized light tothe right, designated
Diagonal relationships refer tosimilarities that exist between certainpairs of elements in different groupsand periods of the periodic table,such as Li and Mg, Be and Al, andB and Si.
A diamagnetic substance has allits electrons paired and is slightlyrepelled by a magnetic field.
Diastereomers are optically activeisomers of a compound, but theirstructures are not mirror images (as are enantiomers).
Diffraction is the dispersion of lightinto its different components as aresult of the interference produced bythe reflection of light from a groovedsurface.
Diffusion refers to the spreading of a substance (usually a gas or liquid) into a region where it is not originallypresent as a result of randommolecular motion.
A dimer is a molecule comprised oftwo simpler formula units, such as
which is a dimer of
Dipole moment, is a measure of the extent to which a separation existsbetween the centers of positive andnegative charge within a molecule. Theunit used to measure dipole moment isthe debye,
Dispersion (London) forces areintermolecular forces associated withinstantaneous and induced dipoles.
In a disproportionation reaction, thesame substance is both oxidized andreduced.
In a double covalent bond, two pairs ofelectrons are shared between bondedatoms. The bond is represented by adouble-dash sign
An E1 reaction is an eliminationreaction in which the rate-determiningstep is unimolecular.
An E2 reaction is an eliminationreaction in which the rate-determiningstep is bimolecular.
Effective nuclear charge, is thepositive charge acting on a particularelectron in an atom. Its value is thecharge on the nucleus, reduced to theextent that other electrons screen theparticular electron from the nucleus.
Effusion is the escape of a gas througha tiny hole in its container.
An electrochemical cell is a device inwhich the electrons transferred in anoxidation reduction reaction are madeto pass through an electrical circuit. (Seealso electrolytic cell and voltaic cell.)
An electrode is a metal surface on which an oxidation reductionequilibrium is established between themetal and substances in solution.
Electrolysis is the decomposition of asubstance, either in the molten state orin an electrolyte solution, by means ofelectric current.
An electrolyte is a substance thatprovides ions when dissolved in water.
An electrolytic cell is an electrochemicalcell in which a nonspontaneousreaction is carried out by electrolysis.
Zeff ,
( ).
3.34 * 10-30 C m.
m,
AlCl3 .Al2Cl6 ,
Electromagnetic radiation is a formof energy propagated as mutuallyperpendicular electric and magneticfields. It includes visible light, infrared,ultraviolet, X ray, and radio waves.
Electromotive force (emf) is thepotential difference between twoelectrodes in a voltaic cell, expressed in volts.
Electron affinity is the energychange associated with the gain of anelectron by a neutral gaseous atom.
Electron capture (EC) is a form ofradioactive decay in which an electronfrom an inner electronic shell is absorbedby a nucleus. In the nucleus the electronis used to convert a proton to a neutron.
An electron configuration is adesignation of how electrons aredistributed among various orbitalsin an atom.
Electronegativity (EN) is a measureof the electron-attracting power of abonded atom; metals have lowelectronegativities, and nonmetalshave high electronegativities.
The electronegativity differencebetween two atoms that are bondedtogether is used to assess the degreeof polarity in the bond.
Electron-group geometry refers tothe geometrical distribution about acentral atom of the electron pairs in its valence shell.
Electron spin is a characteristic ofelectrons giving rise to the magneticproperties of atoms. The twopossibilities for electron spin are and
Electrons are particles carrying thefundamental unit of negative electriccharge. They are found outside thenuclei of all atoms.
Electron-withdrawing substituentsare atoms or groups of atoms thatdraw electron density towardthemselves. Highly electronegativeatoms, such as F, O, N, and Cl, areexamples.
An electrophile contains an electron-attracting region of positive charge (anelectrophilic center) and is a reagentthat forms a bond to its reactionpartner (the nucleophile) by acceptingboth bonding electrons from thatreaction partner.
An electrophilic center in a moleculeis an electron-attracting region ofpositive charge.
In an electrophilic substitutionreaction, an electrophile replacesanother atom or group in a molecule.An example of an electrophilicsubstitution reaction is the replacementof an H atom in benzene with a nitro
group.1NO22
- 12 .+
12
(EA)
An electrostatic potential map depictsthe electron charge distribution in amolecule. The color red is used torepresent the region with the mostnegative charge, and blue representsthe most positive charge.
An element is a substance composedof a single type of atom. It cannot bebroken down into simpler substancesby chemical reactions.
An elementary process is an event that significantly alters a molecule senergy or geometry or produces a new molecule(s). It represents a singlestep in a reaction mechanism.
In an elimination reaction, atoms orgroups that are bonded to adjacentatoms are eliminated as a smallmolecule (e.g., ) and an additionalbond is formed between carbon atoms.
An empirical formula is the simplestchemical formula that can be writtenfor a compound, that is, having thesmallest integral subscripts possible.
Enantiomers (optical isomers) aremolecules whose structures arenonsuperimposable mirror images.The molecules are optically active, that is, able to rotate the plane ofpolarized light.
An endothermic reaction results in a lowering of the temperature of anisolated system or the absorption ofheat by a system that interacts with its surroundings.
The end point is the point in a titrationwhere the indicator used changes color.A properly chosen indicator has its endpoint coming as closely as possible tothe equivalence point of the titration.
Energy is the capacity to do work.(See also work.)
An energy-level diagram is arepresentation of the allowed energystates for the electrons in atoms. Thesimplest energy-level diagram is thatof the hydrogen atom.
The English system of measurementhas the yard as its unit of length, thepound as its unit of mass, and thesecond as its unit of time.
Enthalpy, H, is a thermodynamicfunction used to describe constant-pressure processes: and atconstant pressure,
Enthalpy change, is the differencein enthalpy between two states of asystem. For a chemical reaction carriedout at constant temperature andpressure and with work limited topressure volume work, the enthalpychange is called the heat of reaction atconstant pressure.
An enthalpy diagram is adiagrammatic representation of the enthalpy changes in a process.
Enthalpy (heat) of formation (Seestandard enthalpy of formation.)
Entropy, S, is a thermodynamicproperty related to the number ofenergy levels among which the energyof a system is spread. The greater thenumber of energy levels for a giventotal energy, the greater the entropy.
Entropy change, is the difference inentropy between two states of a system.
An enzyme is a high molar mass proteinthat catalyzes biological reactions.
An equation of state is a mathematicalexpression relating the amount,volume, temperature, and pressure ofa substance (usually applied to gases).
Equilibrium refers to a condition whereforward and reverse processes proceedat equal rates and no further net changeoccurs. For example, amounts ofreactants and products in a reversiblereaction remain constant over time.
The equilibrium constant is thenumerical value of the equilibriumconstant expression.
An equilibrium constant expressiondescribes the relationship among theconcentrations (or partial pressures) of the substances present in a system at equilibrium.
The equivalence point of a titration isthe condition in which the reactantsare in stoichiometric proportions. Theyconsume each other, and neitherreactant is in excess.
An ester is the product of the eliminationof from between an acid and analcohol molecule. Esters have the
general formula .
An ether has the general formula
Eutrophication is the deterioration of afreshwater body caused by nutrientssuch as nitrates and phosphates, whichstimulate the growth of algae, oxygendepletion, and fish kills.
Evaporation is the physical process ofa liquid changing to a vapor. (See alsovaporization.)
In an excited state of an atom, one ormore electrons are promoted to ahigher energy level than in the groundstate. (See also ground state.)
An exothermic reaction produces anincrease in temperature in an isolatedsystem or, for a system that interactswith its surroundings, the evolution of heat.
Expanded valence shell is a term usedto describe Lewis structures in whichcertain atoms in the third or higherperiod of the periodic table appear to require 10 or 12 electrons in theirvalence shells.
R¬O¬R¿.
C O
O
R*R
H2O
S,
An extensive property is one, likemass or volume, whose value dependson the quantity of matter observed.
Extractive metallurgy refers to theprocess of extracting a metal from itsores. Generally this occurs in foursteps. Concentration separates the orefrom waste rock (gangue). Roastingconverts the ore to the metal oxide.Reduction (usually with carbon)converts the oxide to the metal.Refining removes impurities from themetal.
The E, Z system is a system ofnomenclature used to describe themanner in which substituent groupsare attached at a carbon-to-carbondouble bond.
A face-centered cubic (fcc) crystalstructure is one in which the unit cellhas structural units at the eight cornersand in the center of each face of theunit cell. It is derived from the cubicclosest packed arrangement of spheres.
The Fahrenheit temperature scale is based on a value of as themelting point of ice and as the boiling point of water.
A family of elements is a numberedgroup from the periodic table, sometimescarrying a distinctive name. For example,group 17 is the halogen family.
The Faraday constant, F, is the chargeassociated with one mole of electrons,
Fats are triglycerides in which saturatedfatty acid components predominate.The block is that portion of theperiodic table where the process offilling of electron orbitals (aufbauprocess) involves subshells. Theseare the lanthanide and actinideelements.
fcc (See face-centered cubic.)
Ferromagnetism is a property thatpermits certain materials (notably Fe,Co, and Ni) to be made into permanentmagnets. The magnetic moments ofindividual atoms are aligned intodomains. In the presence of a magneticfield, these domains orient themselves toproduce a permanent magnetic moment.
A Fischer projection formula is a two-dimensional representation of athree-dimensional structural formula.It shows how the stereochemistry at a chiral carbon atom is represented in two dimensions, and how thecarbon-chain backbone is arranged on the page.
The first law of thermodynamics,expressed as is analternative statement of the law ofconservation of energy. (See also lawof conservation of energy.)
¢U = q + w,
f
f
96,485 C>mol e-.
212 °F32 °F
A first-order reaction is one for whichthe sum of the concentration-termexponents in the rate equation is 1.
Fission (See nuclear fission.)
A flow battery is a battery in whichmaterials (reactants, products,electrolytes) pass continuously throughthe battery. The battery is simply aconverter of chemical to electrical energy.
Formal charge is the number of outer-shell (valence) electrons in an isolatedatom minus the number of electronsassigned to that atom in a Lewisstructure.
The formation constant, describesequilibrium among a complex ion, thefree metal ion, and ligands.
Formula mass is the mass of a formulaunit of a compound, relative to a massof exactly 12 u for carbon-12.
A formula unit is the smallestcollection of atoms or ions from whichthe empirical formula of a compoundcan be established.
Fractional crystallization(recrystallization) is a method ofpurifying a substance by crystallizingthe pure solid from a saturated solutionwhile impurities remain in solution.
Fractional distillation (See distillation.)
Fractional precipitation is a techniquein which two or more ions in solution,each capable of being precipitated bythe same reagent, are separated by theuse of that reagent.
The Frasch process is a method ofextracting sulfur from underwaterdeposits. It is based on the use ofsuperheated water to melt the sulfur.
Free radicals are highly reactivemolecular fragments containingunpaired electrons.
Freezing is the conversion of a liquid toa solid that occurs at a fixed temperatureknown as the freezing point.
The frequency of a wave motion is thenumber of wave crests or troughs thatpass through a given point in a unit oftime. It is expressed by the unit (e.g., also called a hertz, Hz).
A fuel cell is a voltaic cell in which thecell reaction is the equivalent of thecombustion of a fuel. Chemical energyof the fuel is converted to electricity.
A function of state (state function) is aproperty that assumes a unique valuewhen the state or present condition of asystem is defined. This value isindependent of how the state is attained.
A functional group is an atom orgrouping of atoms attached to ahydrocarbon residue, R. The functionalgroup often confers specific propertiesto an organic molecule.
Gamma ( ) rays are a form ofelectromagnetic radiation of highpenetrating power emitted by certainradioactive nuclei.
In a gas, atoms or molecules aregenerally much more widely separatedthan in liquids and solids. A gasassumes the shape of its container andexpands to fill the container, thus havingneither definite shape nor volume.
The gas constant, R, is the numericalconstant appearing in the ideal gasequation and in severalother equations as well.
In the gauche conformation, themethyl groups are to the left and right of each other.
In a geminal dihalide, a halogen addsacross the double bond of an alkene,and the two halogen atoms are bondedto the same carbon.
The general gas equation is anexpression based on the ideal gasequation and written in the form
Geometric isomerism in organiccompounds refers to the existence of nonequivalent structures (cis andtrans) that differ in the positioning ofsubstituent groups relative to a doublebond. In complexes, the nonequivalentstructures are based on the positions atwhich ligands are attached to themetal center.
Gibbs energy, G, is a thermodynamicfunction designed to produce acriterion for spontaneous change. It is defined through the equation
Gibbs energy change, is the changein Gibbs energy that accompanies aprocess and can be used to indicate thedirection of spontaneous change. For aspontaneous process at constanttemperature and pressure, (Seealso standard Gibbs energy change.)
Glass is a transparent, amorphous solidconsisting of and ions in anetwork of anions. It is made byfusing together a mixture of sodiumand calcium carbonates with sand.
Global warming refers to the warming of Earth that results from an accumulation in the atmosphere of gases such as that absorbinfrared radiation radiated fromEarth s surface.
Graham s law states that the rates ofeffusion or diffusion of two differentgases are inversely proportional to thesquare roots of their molar masses.
The ground state is the lowest energystate for the electrons in an atom ormolecule.
CO2
SiO4
4-Ca2+Na+
¢G 6 0.
G,
G = H - TS.
P2 V2>n2 T2 .=P1 V1>n1 T1
1PV = nRT2
G
A group is a vertical column ofelements in the periodic table. Membersof a group have similar properties.
A half-cell is a combination of anelectrode and a solution. An oxidationreduction equilibrium is established onthe electrode. An electrochemical cell isa combination of two half-cells.
The half-life of a reaction is thetime required for one-half of a reactantto be consumed. In a nuclear decayprocess, it is the time required for one-half of the atoms present in a sample toundergo radioactive decay.
A half-reaction describes one portionof an overall oxidation reductionreaction, either the oxidation or thereduction.
Halogens (group 17) are the mostreactive nonmetals, having the electronconfiguration in the electronicshell of highest principal quantumnumber.
Hard water contains dissolvedminerals in significant concentrations.If the hardness is primarily due to
and associated cations, thewater has temporary hardness. If thehardness is due to anions other than
(e.g., ), the water haspermanent hardness.
hcp (See hexagonal closest packed.)
Heat is a transfer of thermal energy asa result of a temperature difference.
Heat capacity is the quantity of heatrequired to change the temperature ofan object or substance by one degree,usually expressed as or cal Specific heat capacity is the heat capacityper gram of substance, i.e., and molar heat capacity is the heatcapacity per mole, i.e.,
A heat of reaction is energy convertedfrom chemical to thermal (or viceversa) in a reaction. In an isolatedsystem, this energy conversion causesa temperature change, and in a systemthat interacts with its surroundings,heat (q) is either evolved to orabsorbed from the surroundings.
The Heisenberg uncertainty principlestates that, when measuring the positionand momentum of fundamentalparticles of matter, uncertainties in measurement are inevitable.
The Henderson Hasselbalch equationhas the form, [conjugate base]/[acid], in whichstoichiometric concentrations of theweak acid and its conjugate base are used in place of the equilibriumconcentrations. There are limitations on its validity.
Henry s law relates the solubility of agas to the gas pressure maintainedabove a solution of the gaseous solute.
pKa + log=pH
J °C-1 mol-1.
J °C-1 g-1,
°C-1.J °C-1
SO4
2-HCO3
-
HCO3
-
ns2np5
1t1/22
The solubility is directly proportionalto the pressure of the gas above thesolution.
The hertz (Hz) is the SI unit offrequency, equal to
Hess s law states that the enthalpychange for an overall or net process is the sum of enthalpy changes forindividual steps in the process.
Heterocyclic compounds are based onhydrocarbon ring structures in whichone or more C atoms are replaced byatoms such as N, O, or S.
Heterogeneous catalysis is catalyticaction that takes place on a surfaceseparating two phases.
In a heterogeneous mixture,components separate into physicallydistinct regions of differing propertiesand often differing composition.
Hexagonal closest packed is one of the two ways in which spheres can bepacked to minimize the amount of free space or voids among them. Thecrystal structure based on this type of packing is referred to as hcp.
In a high-spin complex, weak crystalfield splitting leads to a maximumnumber of unpaired electrons in the dsubshell of the central metal atom or ion.
Homogeneous catalysis refers to acatalytic reaction taking place in asingle phase.
A homogeneous mixture (solution) is amixture of elements and/or compoundsthat has a uniform composition andproperties within a given sample.However, the composition andproperties may vary from one sample to another.
A homologous series is a group ofcompounds that differ in compositionby some constant unit ( in thecase of alkanes).
Hund s rule (rule of maximummultiplicity) states that wheneverorbitals of equal energy are available,electrons occupy these orbitals singlybefore any pairing of electronsoccurs.
A hybrid orbital is one of a set ofidentical orbitals reformulated frompure atomic orbitals and used todescribe certain covalent bonds.
Hybridization refers to combiningpure atomic orbitals to generate hybridorbitals in the valence bond approachto covalent bonding.
A hydrate is a compound in which afixed number of water molecules isassociated with each formula unit,such as
Hydrides are compounds of hydrogen,usually divided into the categories ofcovalent (e.g., and HCl), ionicH2O
(e.g., LiH and ), and metallic(mostly nonstoichiometric compoundswith the transition metals).
A hydrocarbon is a compoundcontaining the two elements carbonand hydrogen. The C atoms arearranged in straight or branchedchains or ring structures.
A hydrogen bond is an intermolecularforce of attraction in which an H atomcovalently bonded to one atom isattracted simultaneously to anotherhighly nonmetallic atom of the same or a nearby molecule.
In a hydrogenation reaction, H atomsare added to multiple bonds betweencarbon atoms, converting carbon-to-carbon double bonds to single bondsand carbon-to-carbon triple bonds todouble or single bonds. It is a reaction,for example, that converts anunsaturated to a saturated fatty acid.
Hydrolysis is a special name given to acid base reactions in which ionsact as acids or bases. As a result ofhydrolysis, many salt solutions are not pH neutral, that is,
Hydrometallurgy refers tometallurgical procedures where waterand aqueous solutions are used toextract metals from their ores. In thefirst step, leaching, the target metal isobtained in soluble form in aqueoussolution. Other steps include purifyingthe leached solution and depositingthe metal from solution.
Hydronium ion, is the form inwhich protons are found in aqueoussolution. The terms hydrogen ionand hydronium ion are often usedsynonymously.
The hydroxyl group is and isusually found attached to a straight or branched hydrocarbon chain (analcohol) or a ring structure (a phenol).
A hypothesis is a tentative explanationof a series of observations or of anatural law.
An ICE table is a format for organizingthe data in an equilibrium calculation.It is based on the initial concentrationsof reactants and products, changes inconcentrations to attain equilibrium,and equilibrium concentrations.
An ideal (perfect) gas is one whosebehavior can be predicted by the idealgas equation.
Ideal gas constant (See gas constant.)
The ideal gas equation relates thepressure, volume, temperature, andnumber of moles of ideal gas (n)through the expression
An ideal solution has and certain properties (notably vaporpressure) that are predictable from theproperties of the solution components.
¢Hsoln = 0
PV = nRT.
¬OH
H3O*,
pH Z 7.
CaH2 An indicator is an added substancethat changes color at the equivalencepoint in a titration.
The inductive effect refers to theshifting of electron density from oneatom toward another through thechain of bonds that connects them.
Industrial smog is air pollution inwhich the chief pollutants are
mist, and smoke.
Inert complex is the term used todescribe a complex ion in which theexchange of ligands occurs very slowly.
The inert pair effect refers to theeffects on the properties of certainpost-transition elements that resultfrom the presence of a pair of electronsin the s orbital of the valence shells oftheir atoms.
The initial rate of a reaction is the rateof a reaction immediately after thereactants are brought together.
An inorganic compound is anycombination of elements that does notfit the category of organic compound.(See also organic compound.)
An instantaneous rate of reaction isthe exact rate of a reaction at someprecise point in the reaction. It isobtained from the slope of a tangentline to a concentration time graph.
An integrated rate law (equation) isderived from a rate law (equation) bythe calculus technique of integration. Itrelates the concentration of a reactant(or product) to elapsed time from thestart of a reaction. The equation hasdifferent forms depending on the orderof the reaction.
An intensive property is independent ofthe quantity of matter involved in theobservation. Density and temperatureare examples of intensive properties.
An interhalogen compound is acovalent compound between two ormore halogen elements, such as ICland
An intermediate is the product of one reaction that is consumed in afollowing reaction in a process thatproceeds through several steps.
The internal energy, U, of a system is the total energy attributed to theparticles of matter and theirinteractions within a system.
An ion is a charged species consistingof a single atom or a group of atoms.It is formed when a neutral atom or acovalently bonded group of atomseither gains or loses electrons.
Ion exchange is a process in which ionsheld to the surface of an ion exchangematerial are exchanged for other ionsin solution. For example, maybe exchanged for and or
may be exchanged for SO4
2-.OH-
Mg2+,Ca2+Na+
BrF3.
H2SO4SO3(g),SO2(g),
s
An ion pair is an association of acation and an anion in solution. Suchcombinations, when they occur, canhave a significant effect on solutionequilibria.
An ion product, is formulated inthe same manner as a solubility productconstant, but with nonequilibriumconcentration terms. A comparison of
and provides a criterion forprecipitation from solution.
The ion product of water, is theproduct of and in purewater or in an aqueous solution. Thisproduct has a unique value thatdepends only on temperature. At
An ionic bond results from thetransfer of electrons between metaland nonmetal atoms. Positive andnegative ions are formed and heldtogether by electrostatic attractions.
An ionic compound is a compoundconsisting of positive and negativeions that are held together byelectrostatic forces of attraction.
Ionic radius is the radius of a sphericalion. It is the atomic radius associatedwith an element in its ionic compounds.
The first ionization energy, is theenergy required to remove the mostloosely held electron from a gaseousatom. The second ionization energy, is the energy required to remove anelectron from a gaseous unipositiveion, and so on.
An irreversible process takes place inone or several finite steps such that thesystem is not in equilibrium with itssurroundings.
The isoelectric point, pI, of an aminoacid is the pH at which the dipolarstructure or zwitterion predominates.
Isoelectronic species have the samenumber of electrons (usually in thesame configuration). and Ne are isoelectronic, as are CO and
An isolated system is one thatexchanges neither energy nor matter with its surroundings.
Isomers are two or more compoundshaving the same formula but differentstructures and therefore differentproperties.
Isotopes of an element are atoms withdifferent numbers of neutrons in theirnuclei. That is, isotopes of an elementhave the same atomic numbers butdifferent mass numbers.
Isotopic mass (See nuclidic mass.)
IUPAC (or IUC) refers to theInternational Union of Pure andApplied Chemistry.
is the relationship among theconcentrations of the reactants andKc
products in a reversible reaction atequilibrium. Concentrations areexpressed as molarities.
the partial pressure equilibriumconstant, is the relationship that existsamong the partial pressures of gaseousreactants and products in a reversiblereaction at equilibrium. Partialpressures are expressed in atm.
The Kelvin temperature is an absolutetemperature. That is, the lowestattainable temperature is
(the temperature at whichmolecular motion ceases). Kelvin andCelsius temperatures are related throughthe expression T
A ketone has the general formula
.
A kilopascal (kPa) is a unit of pressureequal to 1000 pascals (Pa) or
The standard atmosphereof pressure is 101.325 kPa.
Kinetic energy is energy of motion.The kinetic energy of an object withmass m and velocity u is
The kinetic-molecular theory of gasesis a model for describing gas behavior.It is based on a set of assumptions andyields equations from which variousproperties of gases can be deduced.
Labile complex is the term used todescribe a complex ion in which arapid exchange of ligands occurs.
The lanthanide contraction refers tothe decrease in atomic size in a series ofelements in which an subshell fills withelectrons (an inner transition series). Itresults from the ineffectiveness of electrons in shielding outer-shell electronsfrom the nuclear charge of an atom.
The lanthanides are the elementscharacterized by a
partially filled subshell in theiratoms. Because lanthanum resemblesthem, La is generallyconsidered together with them.
Lattice energy is the quantity ofenergy released in the formation of one mole of a crystalline ionic solidfrom its separated gaseous ions.
Gay-Lussac s law of combiningvolumes states that, when compared atthe same temperature and pressure, thevolumes of gases involved in a reactionare in the ratio of small whole numbers.
The law of conservation of energystates that energy can neither be creatednor destroyed in ordinary processes.
The law of conservation of mass statesthat the total mass of the products of a chemical reaction is the same as thetotal mass of the reactants enteringinto the reaction.
1Z = 572
4f1Z = 58 - 712
f
f
K.E. = 12 mu2.
1000 N>m-2.
C
O
R*R
(K) = t(°C) + 273.15.
-273.15 °C0 K =
Kp ,
The law of constant composition(definite proportions) states that allsamples of a compound have the same composition, that is, the sameproportions by mass of the constituentelements.
The law of multiple proportionsstates that if two elements form two or more compounds, the masses of one element combined with a fixedmass of the second are in the ratio of small whole numbers when thedifferent compounds are compared.
The leaving group is the speciesexpelled from an electrophilic moleculefollowing attack by a nucleophile.
Le Châtelier s principle states thatan action that tends to change thetemperature, pressure, or concentrationsof reactants in a system at equilibriumstimulates a response that partiallyoffsets the change while a newequilibrium condition is established.
Levorotatory means the ability torotate the plane of polarized lightto the left, designated
Lewis acid (See acid.)
Lewis base (See base.)
A Lewis structure is a combination ofLewis symbols that depicts the transferor sharing of electrons in a chemicalbond.
In the Lewis symbol of an element,valence electrons are represented bydots placed around the chemicalsymbol of the element.
The Lewis theory refers to a descriptionof chemical bonding through Lewissymbols and Lewis structures inaccordance with a particular set of rules.
Ligands are the groups that arecoordinated (bonded) to the centralatom in a complex.
The limiting reactant (reagent)in a reaction is the reactant that isconsumed completely. The quantity of product(s) formed depends on thequantity of the limiting reactant.
Line-angle formulas are shorthandrepresentations of organic molecules inwhich bond lines are drawn, butchemical symbols are written only forelements other than carbon andhydrogen.
A line spectrum is produced from theemission of light produced from excitedatom or ions. The spectrum containslines at discrete wavelengths whicharise from the transition of an electronfrom one energy level to another.
Lipids include a variety of naturallyoccurring substances (e.g., fats andoils) sharing the property of solubilityin solvents of low polarity [such as in
and ].(C2H5)2OC6H6,CCl4,CHCl3,
1-2.
In a liquid, atoms or molecules are inclose proximity (although generallynot as close as in a solid). A liquidoccupies a definite volume, but has the ability to flow and assume theshape of its container.
London forces (See dispersion forces.)
A lone pair is a pair of electrons foundin the valence shell of an atom and notinvolved in bond formation.
In a low-spin complex, strong crystalfield splitting leads to a minimumnumber of unpaired electrons in the dsubshell of the central metal atom or ion.
Magic numbers is a term used todescribe numbers of protons andneutrons that confer a special stabilityto an atomic nucleus.
The main-group elements are those inwhich s or p subshells are being filledin the aufbau process. They are alsoreferred to as the s-block and p-blockelements. They are found in groups1, 2, and 13 18 in the periodic table(the A groups).
A manometer is a device used tomeasure the pressure of a gas, usuallyby comparing the gas pressure withbarometric pressure.
Mass describes the quantity of matterin an object.
The mass number, A, is the total of thenumber of protons and neutrons in thenucleus of an atom.
A mass spectrometer (massspectrograph) is a device used toseparate and to measure the quantitiesand masses of different ions in a beamof positively charged gaseous ions.
Matter is anything that occupies space,has the property known as mass, anddisplays inertia.
Melting is the transition of a solid to aliquid and occurs at the melting point.The melting point and freezing pointof a substance are identical.
A meta (m-) isomer has twosubstituents on a benzene ringseparated by one C atom.
Metabolism refers to the totality of thechemical reactions occurring in livingorganisms.
A metal is an element whose atomshave small numbers of electrons in theoutermost electronic shell. Removal ofan electron(s) from a metal atom occurswithout great difficulty, producing apositive ion (cation). Metals generallyhave a lustrous appearance, aremalleable and ductile, and are able toconduct heat and electricity.
Metal carbonyls are complexes withd-block metals as central atoms andCO molecules as ligands, e.g., Ni(CO)4.
Metallic radius is one-half the distancebetween the centers of adjacent atomsin a solid metal.
A metalloid is an element that maydisplay both metallic and nonmetallicproperties under the appropriateconditions.
A millimeter of mercury (mmHg)is a unit of pressure, usually applied to gases. For example, standardatmospheric pressure is equal tothe pressure exerted by a 760-mmcolumn of mercury.
A millimole (mmol) is one-thousandthof a mole (0.001 mol). It is especiallyuseful in titration calculations.
A mixture is any sample of matter thatis not pure, that is, not an element orcompound. The composition of amixture, unlike that of a substance, canbe varied. Mixtures are eitherhomogeneous or heterogeneous.
Moderator control slows downenergetic neutrons from a fissionprocess so that they are able to induceadditional fission.
Molality, m, is a solution concentrationexpressed as the amount of solute, inmoles, divided by the mass of solvent,in kg.
Molar mass, M, is the mass of onemole of atoms, formula units, ormolecules of a substance.
A mole is an amount of substancecontaining Avogadro s number
of atoms, formulaunits, or molecules.
Mole fraction describes a mixture in terms of the fraction of all themolecules that are of a particular type.It is the amount of one component, inmoles, divided by the total amount ofall the substances in the mixture.
A mole percent is a mole fractionexpressed on a percentage basis, that is, mole
A molecular compound is a compoundcomprised of discrete molecules.
A molecular formula denotes thenumbers of the different atoms presentin a molecule. In some cases themolecular formula is the same as theempirical formula; in others it is anintegral multiple of that formula.
Molecular geometry refers to thegeometric shape of a molecule orpolyatomic ion. In a species in whichall electron pairs are bond pairs, themolecular geometry is the same asthe electron-group geometry. In othercases, the two properties are relatedbut not the same.
Molecular mass is the mass of amolecule relative to a mass of exactly12 u for carbon-12.
fraction * 100%.
16.02214 * 10232
Molecular orbital theory describes the covalent bonds in a molecule byreplacing atomic orbitals of thecomponent atoms by molecularorbitals belonging to the molecule as awhole. A set of rules is used to assignelectrons to these molecular orbitals,thereby yielding the electronicstructure of the molecule.
A molecule is a group of bondedatoms held together by covalent bondsand existing as a separate entity. Amolecule is the smallest entity havingthe characteristic proportions of theconstituent atoms present in asubstance.
A monodentate ligand is a ligand thatis able to attach to a metal center in acomplex at only one position andusing just one lone pair of electrons.
A monosaccharide is a single, simplemolecule having the structural featuresof a carbohydrate. It can also be calleda simple sugar.
A multiple covalent bond is a bond in which more than two electrons areshared between the bonded atoms.
A natural law is a concise statement,often in mathematical terms, thatsummarizes observations of certainnatural phenomena.
The Nernst equation is used to relateand the activites of the
reactants and products in a cell reaction.
A net ionic equation represents areaction between ions in solution insuch a way that all nonparticipant(spectator) ions are eliminated fromthe equation. The equation must bebalanced both atomically and for netelectric charge.
A network covalent solid is a substancein which covalent bonds extendthroughout the crystal, making thecovalent bond both an intramolecularand an intermolecular force.
In a neutralization reaction, an acidand a base react in stoichiometricproportions, so that there is no excess ofeither acid or base in the final solution.The products are water and a salt.
Neutrons are electrically neutralfundamental particles of matter foundin all atomic nuclei except that of thesimple hydrogen atom, protium,
The neutron number is the number ofneutrons in the nucleus of an atom. Itis equal to the mass number (A) minusthe atomic number (Z).
Noble gases are elements whoseatoms have the electron configuration
in the electronic shell of highestprincipal quantum number. (Thenoble gas helium has theconfiguration )1s2.
ns2np6
1H.
Ecell°Ecell ,
A nonelectrolyte is a substance that is essentially non-ionized, both in thepure state and in solution.
A nonmetal is an element whose atomstend to gain small numbers of electronsto form negative ions (anions) with theelectron configuration of a noble gas.Nonmetal atoms may also alter theirelectron configurations by sharingelectrons. Nonmetals are mostly gases,liquid (bromine), or low melting pointsolids and are very poor conductors ofheat and electricity.
A nonspontaneous process is one that will not occur naturally. A nonspontaneous process can bebrought about only by interventionfrom outside the system, as in the useof electricity to decompose a chemicalcompound (electrolysis).
The normal boiling point is thetemperature at which the vaporpressure of a liquid is 1 atm. It is thetemperature at which the liquid boilsin a container open to the atmosphereat a pressure of 1 atm.
A nuclear equation represents thechanges that occur during a nuclearprocess. The target nucleus andbombarding particle are representedon the left side of the equation, and theproduct nucleus and ejected particleon the right side.
Nuclear fission is a radioactive decayprocess in which a heavy nucleusbreaks up into two lighter nuclei and several neutrons, accompanied by the release of energy.
In nuclear fusion small atomic nucleiare fused into larger ones, with some oftheir mass being converted to energy.
Nucleic acids are cell componentscomprised of purine and pyrimidinebases, pentose sugars, and phosphoricacid.
A nucleophile is a reactant that seeksout a center of positive charge as apoint of attack in a chemical reaction.
A nucleophilic substitution reactionis a reaction between a nucleophileand an electrophile. The nucleophileattacks at a positive center on theelectrophile, and the leaving group isejected from another point.
Nucleophilicity is a measure of howreadily (how fast) a nucleophile attacksan electrophilic carbon atom bearing aleaving group.
Nuclide is a term used to designate anatom with a specific atomic numberand mass number. It is represented bythe symbolism
An octet refers to eight electrons in theoutermost (valence) electronic shell ofan atom in a Lewis structure.
The octet rule states that the numberof electrons associated with bond pairsand lone pairs of electrons for each ofthe Lewis symbols (except H) in aLewis structure will be eight (an octet).
Oils are triglycerides in whichunsaturated fatty acid componentspredominate.
Olefins are organic compounds thatcontain one or more carbon-to-carbondouble bonds.
Oligosaccharides are carbohydratesconsisting of two to ten monosaccharideunits. (See also sugar.)
An open system is one that canexchange both matter and energywith its surroundings.
Optical isomerism results from the presence of a chiral atom in astructure, leading to a pair of opticalisomers that differ only in the directionthat they rotate the plane of polarizedlight. (See also enantiomers.)
Optical isomers, also calledenantiomers (nonsuperimposablemirror images), are isomers that differonly in the direction they rotate theplane of polarized light.
An orbital is a mathematical functionused to describe regions in an atomwhere the electron charge density orthe probability of finding an electron ishigh. The several kinds of orbitals (s, p,
d, differ from one another in theshapes of the regions of high electroncharge density they describe.
An orbital diagram is a representationof an electron configuration in whichthe most probable orbital designationand spin of each electron in the atomare indicated.
The order of a reaction relates to theexponents of the concentration termsin the rate law for a chemical reaction.The order can be stated with respect toa particular reactant (first order in A,second order in B, ) or, morecommonly, as the overall order. Theoverall order is the sum of theconcentration-term exponents.
An organic compound is made upof carbon and hydrogen or carbon,hydrogen and a small number of otherelements, such as oxygen, nitrogen,and sulfur.
An ortho (o-) isomer has twosubstituents attached to adjacent Catoms in a benzene ring.
Osmosis is the net flow of solventmolecules through a semipermeablemembrane, from a more dilutesolution (or from the pure solvent) into a more concentrated solution.
Osmotic pressure is the pressure thatwould have to be applied to a solutionto stop the passage through a
Á
f, Á )
semipermeable membrane of solventmolecules from the pure solvent.
An overall reaction or overallequation is the overall or net changethat occurs when a process is carriedout in more than one step.
An overpotential is the voltage inexcess of the theoretical value requiredto produce a particular electrodereaction in electrolysis.
Oxidation is a process in whichelectrons are lost and the oxidationstate of some atom increases.(Oxidation can occur only incombination with reduction.)
In an oxidation reduction (redox)reaction certain atoms undergochanges in oxidation state. Thesubstance containing atoms whoseoxidation states increase is oxidized.The substance containing atoms whoseoxidation states decrease is reduced.
An oxidation state relates to thenumber of electrons an atom loses,gains, or shares in combining withother atoms to form molecules orpolyatomic ions.
An oxidizing agent (oxidant) makespossible an oxidation process by itselfbeing reduced.
An oxoacid is an acid in which anionizable hydrogen atom(s) is bondedthrough an oxygen atom to a centralatom, that is, Other groupsbonded to the central atom are eitheradditional groups or O atoms(or in a few cases H atoms).
An oxoanion is a polyatomic anioncontaining a nonmetal, such as Cl, N,P, or S, in combination with somenumber of oxygen atoms.
Pairing energy is the energyrequirement to force an electron into an orbital that is already occupiedby one electron.
A para isomer has twosubstituents located opposite to one another on a benzene ring.
A paramagnetic substance has one ormore unpaired electrons in its atoms ormolecules. It is attracted into amagnetic field.
A partial pressure is the pressureexerted by an individual gas in amixture, independently of other gases.Each gas in the mixture expands to fillthe container and exerts its own partialpressure.
A pascal (pa) is a pressure of one
The Pauli exclusion principle statesthat no two electrons may have all fourquantum numbers alike. This limitsoccupancy of an orbital to twoelectrons with opposing spins.
N>m2.
1p-2
¬OH
E¬O¬H.
The block is that portion of theperiodic table in which the filling ofelectron orbitals (aufbau process)involves p subshells.
A peptide bond is formed by theelimination of a water molecule frombetween two amino acid molecules.The H atom comes from the group of one amino acid and the
group, from the group of the other acid.
The percent ionization of a weak acid ora weak base is the percent of its moleculesthat ionize in an aqueous solution.
Percent natural abundances refer tothe relative proportions, expressed aspercentages by number, in which theisotopes of an element are found innatural sources.
Percent yield is the percent of thetheoretical yield of product that isactually obtained in a chemicalreaction. (See also actual yield andtheoretical yield.)
A perfect gas is one whose behaviorcan be predicted by the ideal gasequation. It is also used to describe a gas whose molecules are pointmasses that do not interact with one another. (See also ideal gas.)
A period is a horizontal row of theperiodic table. All members of a periodhave atoms with the same highestprincipal quantum number.
The periodic law refers to the periodicrecurrence of certain physical andchemical properties when the elementsare considered in terms of increasingatomic number.
The periodic table is an arrangementof the elements, by atomic number, inwhich elements with similar physicaland chemical properties are groupedtogether in vertical columns.
Permanent hard water (See hard water.)
The peroxide ion has the structure
.
pH is a shorthand designation forin a solution. It is defined
as
A phase diagram is a graphicalrepresentation of the conditions oftemperature and pressure at whichsolids, liquids, and gases (vapors)exist, either as single phases or statesof matter or as two or more phases inequilibrium.
A phenol has the functional groupas part of an aromatic
hydrocarbon structure.
A phenyl group is a benzene ring fromwhich one H atom has been removed:
The photoelectric effect is theemission of electrons by certain
materials when their surfaces arestruck by electromagnetic radiation of the appropriate frequency.
A photon is a particle of light. The energy of a beam of light isconcentrated into these photons.
In a physical change, one or morephysical properties of a sample ofmatter change, but the compositionremains unchanged.
A physical property is a characteristicthat a substance can display withoutundergoing a change in itscomposition.
A pi ( ) bond results from the side-to-side overlap of p orbitals, producinga high electron charge density aboveand below the line joining the bondedatoms.
Pig iron is an impure form of iron(about 95% Fe and 3 4% C, togetherwith small quantities of Mn, Si, and P)produced in a blast furnace.
pK is a shorthand designation for anionization constant: pKvalues are useful when comparing therelative strengths of acids or bases.
Planck s constant, h, is theproportionality constant that relatesthe energy of a photon of light to itsfrequency. Its value is
Plaster of Paris, is a
hemihydrate of calcium sulfateobtained by heating gypsum,
It is a widely usedmaterial in the construction industry.
pOH is a shorthand designation forin a solution:
In a polar covalent bond a separationexists between the centers of positiveand negative charge in the bond.
In a polar molecule, the presence ofone or more polar covalent bondsleads to a separation of the positiveand negative charge centers for themolecule as a whole. A polar moleculehas a resultant dipole moment.
Polarizability describes the ease withwhich the electron cloud in an atom ormolecule can be distorted in an electricfield, that is, the ease with which adipole can be induced.
A polyatomic ion is a combination oftwo or more covalently bonded atomsthat exists as an ion.
A polydentate ligand is capable ofdonating more than a single electronpair to the metal center of a complex,from different atoms in the ligand and todifferent sites in the geometric structure.
In a polyhalide ion two or morehalogen atoms are covalently bondedinto a polyatomic anion, e.g., I3
-.
- log[OH-].pOH =[OH-]
CaSO4# 2 H2O.
CaSO4# 1
2 H2O,
6.626 * 10-34 J s.
pK = - logK.
P
Polymorphism refers to the existenceof a solid substance in more than onecrystalline form.
In a polypeptide, a large number ofamino acid units join together throughpeptide bonds.
A polyprotic acid is capable of losing more than a single proton permolecule in acid base reactions.Protons are lost in a stepwise fashion,with the first proton being the mostreadily lost.
A polysaccharide is a carbohydrate(such as starch or cellulose) consistingof more than ten monosaccharide units.
Positional isomers differ in the positionon a hydrocarbon chain or ring where afunctional group(s) is attached.
A positron ( ) is a positive electronemitted as a result of the conversion ofa proton to a neutron in a radioactivenucleus.
Potential energy is energy due toposition or arrangement. It is the energyassociated with forces of attraction andrepulsion between objects.
The term ppb (parts per billion) refersto the number of parts of a componentto one billion parts of the medium inwhich it is found.
The term ppm (parts per million)refers to the number of parts of acomponent to one million parts ofthe medium in which it is found.
The term ppt (parts per trillion) refersto the number of parts of a componentto one trillion parts of the medium inwhich it is found.
A precipitate is an insoluble solid thatdeposits from a solution as a result of achemical reaction.
Precision is the degree ofreproducibility of a measuredquantity the closeness of agreementamong repeated measurements.
Pressure is a force per unit area.Applied to gases, pressure is mosteasily understood in terms of theheight of a liquid column that canbe maintained by the gas.
Pressure volume work is workassociated with the expansion orcompression of gases.
A primary carbon is attached to oneother carbon atom.
A primary battery produces electricityfrom a chemical reaction that cannotbe reversed. As a result the batterycannot be recharged.
A primary color is one of a set ofcolors that when added together aslight produce white light. Subtractivemixing leads to an absence of color(black). Red, yellow, and blue are aset of primary colors.
B*
Hydrogen atoms attached to a primarycarbon atom are called primaryhydrogen atoms.
Primary structure refers to the sequenceof amino acids in the polypeptide chainsthat make up a protein.
A principal electronic shell (level)refers to the collection of all orbitalshaving the same value of the principalquantum number, n. For example, the3s, 3p, and 3d orbitals comprise thethird principal shell
The products are the substancesformed in a chemical reaction.
Properties are qualities or attributesthat can be used to distinguish onesample of matter from others.
A protein is a large polypeptide, thatis, having a molecular mass of 10,000 uor more.
In a protic solvent the molecules have hydrogen atoms bonded toelectronegative atoms, such as oxygenor nitrogen.
A proton acceptor is a base in theBrønsted Lowry acid base theory.
A proton donor is an acid in theBrønsted Lowry acid base theory.
Proton number (See atomic number.)
Protons are fundamental particlescarrying the basic unit of positiveelectric charge and found in the nuclei of all atoms.
Pyrometallurgy is the traditionalapproach to extractive metallurgy thatuses dry solid materials heated to hightemperatures. (See also extractivemetallurgy and hydrometallurgy.)
Qualitative cation analysis is alaboratory method, based on a varietyof solution equilibrium concepts, fordetermining the presence or absence of certain cations in a sample.
A quantum refers to a discrete unit ofenergy that is the smallest quantity bywhich the energy of a system canchange.
Quantum numbers are integralnumbers whose values must bespecified in order to solve theequations of wave mechanics. Threedifferent quantum numbers arerequired: the principal quantum number,n; the orbital angular momentumquantum number, l; and the magneticquantum number, The permittedvalues of these numbers areinterrelated.
A quaternary carbon is attached tofour carbon atoms.
Quaternary structure is the highestorder structure that is found in someproteins. It describes how separatepolypeptide chains may be assembledinto a larger, more complex structure.
A racemic mixture is a mixturecontaining equal amounts of theenantiomers of an optically activesubstance.
A rad is a quantity of radiation able to deposit of energy perkilogram of matter.
A radial wave function, R(r), is the partof a wave function that depends onlyon the distance r when the Schrödingerwave equation is expressed in sphericalpolar coordinates. (See also angularwave function.)
Radical (See free radical.)
The radioactive decay law states thatthe rate of decay of a radioactivematerial the activity, A is directlyproportional to the number of atomspresent.
A radioactive decay series is asuccession of individual steps wherebyan initial radioactive isotope (e.g., )is ultimately converted to a stableisotope (e.g., ).
Radioactivity is a phenomenon inwhich small particles of matter ( or particles) and/or electromagneticradiation ( rays) are emitted byunstable atomic nuclei.
A random error is an error made by the experimenter in performing an experimental technique ormeasurement, such as the error inestimating a temperature reading on a thermometer.
Raoult s law states that the vaporpressure of a solution component isequal to the product of the vaporpressure of the pure liquid and itsmole fraction in solution:
The rate constant, k, is theproportionality constant in a rate lawthat permits the rate of a reaction to be related to the concentrations of thereactants.
A rate-determining step in a reactionmechanism is an elementary processthat is instrumental in establishing the rate of the overall reaction, usuallybecause it is the slowest step in themechanism.
The rate law (rate equation) for areaction relates the reaction rate to the concentrations of the reactants. Ithas the form:
The rate of reaction describes how fastreactants are consumed and productsare formed, usually expressed aschange of concentration per unit time.
Reactants are the substances that enterinto a chemical reaction. This term isoften applied to all the substancesinvolved in a reversible reaction, but it
k[A]m [B]nÁ .=rate
xA PAo .=PA
g
ba
206Pb
238U
1 * 10-2 J
can also be limited to the substancesthat appear on the left side of a chemicalequation the starting substances.(Substances on the right side of theequation are usually called products.)
A reaction intermediate is a speciesformed in one elementary reaction in a reaction mechanism and consumedin a subsequent one. As a result, thespecies does not appear in theequation for the overall reaction.
A reaction mechanism is a set ofelementary steps or processes bywhich a reaction is proposed to occur.The mechanism must be consistentwith the stoichiometry and rate law of the overall reaction.
A reaction profile is a graphicalrepresentation of a chemical reactionin terms of the energies of the reactants,activated complex(es), and products.
The reaction quotient, Q, is a ratio of concentration terms (or partialpressures) having the same form as anequilibrium constant expression, butusually applied to nonequilibriumconditions.
In a rearrangement reaction, amolecule is converted into another of its isomeric forms.
Recrystallization (See fractionalcrystallization.)
A reducing agent (reductant) makespossible a reduction process by itselfbecoming oxidized.
A reducing sugar is one that is ableto reduce to red, insoluble
The sugar must have availablean aldehyde group, which is oxidizedto an acid.
A reduction process is one in whichelectrons are gained and theoxidation state of some atomdecreases. (Reduction can only occurin combination with oxidation.) (Seealso extractive metallurgy.)
Refining (See extractive metallurgy.)
A rem is a unit of radiation related to therad, but taking into account the varyingeffects on biological matter of differenttypes of radiation of the same energy.
Representative elements (Seemain-group elements.)
Resonance occurs when two or moreplausible Lewis structures can bewritten for a species. The true structureis a composite or hybrid of thesedifferent contributing structures.
Reverse osmosis is the passagethrough a semipermeable membraneof solvent molecules from a solution intoa pure solvent. It can be achieved byapplying to the solution a pressure in excess of its osmotic pressure.
A reversible process is one that can bemade to reverse direction by just an
Cu2O.Cu2+(aq)
infinitesimal change in a systemproperty.
Ribonucleic acid (RNA), through itsmessenger RNA (mRNA) and transferRNA (tRNA) forms, is involved in thesynthesis of proteins.
Roasting (See extractive metallurgy.)
The root-mean-square speed is thesquare root of the average of thesquares of the speeds of all the gasmolecules in a gaseous sample.
The system is used to indicate the arrangement of the four groupsbonded to a chiral center and toprovide names that distinguishbetween optical isomers.
A salt bridge is a device (a U-tubefilled with a salt solution) used to jointwo half-cells in an electrochemicalcell. The salt bridge permits the flow of ions between the two half-cells.
The salt effect is that of ions differentfrom those directly involved in asolution equilibrium. The salt effectis also known as the diverse oruncommon ion effect.
Salts are ionic compounds in whichhydrogen atoms of acids are replacedby metal ions. Salts are produced bythe neutralization of acids with bases.
Saponification is the hydrolysis of a triglyceride by a strong base. Theproducts are glycerol and a soap.
Saturated hydrocarbon moleculescontain only single bonds betweencarbon atoms.
A saturated solution is one thatcontains the maximum quantity ofsolute that is normally possible at thegiven temperature.
The s block refers to the portion of theperiodic table in which the filling ofelectron orbitals (aufbau process)involves the s subshell of the electronicshell of highest principal quantumnumber.
The Schrödinger equation describesthe electron in a hydrogen atom as a matter wave. Solutions to theSchrödinger equation are called wave functions.
The scientific method refers to thegeneral sequence of activitiesobservation, experimentation, and the formulation of hypotheses, laws,and theories that lead to theadvancement of scientific knowledge.
The second law of thermodynamicsrelates to the direction of spontaneouschange. One statement of the law is thatall spontaneous processes produce anincrease in the entropy of the universe.
A secondary battery produceselectricity from a reversible chemicalreaction. When electricity is passed
through the battery in the reversedirection the battery is recharged.
A secondary carbon is attached to twoother carbon atoms.
A secondary color is the complement of a primary color. When light of aprimary color and its complement(secondary) color are added, the result iswhite light. When they are subtracted,the result is an absence of color (black).
The secondary structure of a proteindescribes the structure or shape of apolypeptide chain, for example, acoiled helix.
A second-order reaction is one forwhich the sum of the concentration-term exponents in the rate equation is 2.
Self-ionization is an acid basereaction in which one molecule acts as an acid and donates a proton toanother molecule of the same kindacting as a base.
The shielding effect refers to the effectof inner-shell electrons in shielding orscreening outer-shell electrons fromthe full effects of the nuclear charge. In effect the inner electrons partiallyreduce the nuclear charge. (See alsoeffective nuclear charge.)
A side reaction is a reaction thatproduces an undesired or unexpectedproduct and accompanies a reactionintended to produce something else.
A sigma ( ) bond results from theend-to-end overlap of simple orhybridized atomic orbitals along thestraight line joining the nuclei of thebonded atoms.
Significant figures are those digits inan experimentally measured quantitythat establish the precision with whichthe quantity is known.
A silicone is an organosilicon polymercontaining bonds.
Simultaneous reactions are two or morereactions that occur at the same time.
A single covalent bond results fromthe sharing of one pair of electronsbetween bonded atoms. It isrepresented by a single dash sign
A skeletal structure is an arrangementof atoms in a Lewis structure tocorrespond to the actual arrangementfound by experiment.
Slaked lime is a common name forcalcium hydroxide,
Smog is the general term used to referto a condition in which polluted airreduces visibility, causes stinging eyesand breathing difficulties, andproduces additional minor and majorhealth problems. (See also industrialsmog and photochemical smog.)
is the designation for anucleophilic substitution reaction inSN1
Ca(OH)2.
(¬ ).
O¬Si¬O
S
which the rate-determining step isunimolecular.
is the designation for a nucleophilicsubstitution reaction in which the rate-determining step is bimolecular.
Soaps are the salts of fatty acids, e.g.,where the R group is a
hydrocarbon chain containing from 3to 21 C atoms. Sodium and potassiumsoaps are the common soaps used ascleansing agents.
Solders are low-melting alloys usedfor joining wires or pieces of metal.They usually contain metals such asSn, Pb, Bi, and Cd.
In a solid, atoms or molecules are in close contact, often in a highlyorganized arrangement. A solid has adefinite shape and occupies a definitevolume. (See also crystal.)
The solubility of a substance is theconcentration of its saturated solution.
The solubility product constant, is the equilibrium constant thatdescribes the formation of a saturatedsolution of a slightly soluble ioniccompound. It is the product of ionicconcentration terms, with each termraised to an appropriate power.
A solute is a solution component thatis dissolved in a solvent. A solutionmay have several solutes, with thesolutes generally present in lesseramounts than is the solvent.
Solution (See homogeneous mixture.)
The solvent is the solution componentin which one or more solutes aredissolved. Usually the solvent ispresent in greater amount than are the solutes and determines the state ofmatter in which the solution exists.
An sp hybrid orbital is one of the pairof orbitals formed by the hybridizationof one s and one p orbital. The anglebetween the two orbitals is
An hybrid orbital is one of thethree orbitals formed by thehybridization of one s and two porbitals. The angle between any two of the orbitals is
An hybrid orbital is one of thefour orbitals formed by thehybridization of one s and three porbitals. The angle between any two of the orbitals is the tetrahedralangle
An hybrid orbital is one of the five orbitals formed by thehybridization of one s, three p, and oned orbital. The five orbitals are directedto the corners of a trigonal bipyramid.
An hybrid orbital is one of the sixorbitals formed by the hybridization ofone s, three p, and two d orbitals. Thesix orbitals are directed to the cornersof a regular octahedron.
sp3d2
sp3d
109.5°.
sp3
120°.
sp2
180°.
Ksp ,
RCOO-Na+,
SN2
spd notation is a method ofdescribing electron configurations in which the numbers of electronsassigned to each orbital are denoted assuperscripts. For example, the electronconfiguration of Cl is
The specific heat of a substance is thequantity of heat required to change the temperature of one gram of thesubstance by one degree Celsius.
Spectator ions are ionic species that arepresent in a reaction mixture but do not take part in the reaction. They areusually eliminated from a chemicalequation.
The spectrochemical series is aranking of ligand abilities to produce a splitting of the d energy level of acentral metal ion in a complex ion.
Speed of light, c, has a value of
A spontaneous (natural) process isone that is able to take place in asystem left to itself. No external actionis required to make the process go,although in some cases the processmay take a very long time.
Stalactites and stalagmites arelimestone formations inlimestone caves produced by the slowdecomposition of
A standard cell potential, is thevoltage of an electrochemical cell inwhich all species are in their standardstates. (See also cell potential.)
Standard conditions of temperatureand pressure (STP) refers to a gasmaintained at a temperature of exactly
(273.15 K) and 760 mmHg (1 atm).
A standard electrode potential, is the electric potential that developson an electrode when the oxidized and reduced forms of some substanceare in their standard states. Tabulateddata are expressed in terms of thereduction process, that is, standardelectrode potentials are standardreduction potentials.
The standard enthalpy of formation,of a substance is the enthalpy
change that occurs in the formation of1 mol of the substance in its standardstate from the reference forms of itselements in their standard states. Thereference forms of the elements aretheir most stable forms at the giventemperature and 1 bar pressure.
The standard enthalpy of reaction,is the enthalpy change of a
reaction in which all reactants andproducts are in their standard states.
Standard Gibbs energy change, is the Gibbs energy change of a processwhen the reactants and productsare all in their standard states. Theequation relating standard free energy
The standard Gibbs energy offormation, is the standard freeenergy change associated with theformation of 1 mol of compound fromits elements in their most stable formsat 1 bar pressure.
The standard hydrogen electrode(SHE) is an electrode at whichequilibrium is established between
and onan inert (Pt) surface. The standardhydrogen electrode is arbitrarilyassigned an electrode potential ofexactly 0 V.
The standard molar entropy isthe absolute entropy evaluated whenone mole of a substance is in itsstandard state at a particulartemperature.
The standard state of a substancerefers to that substance when it ismaintained at 1 bar pressure and at thetemperature of interest. For a gas it isthe (hypothetical) pure gas behavingas an ideal gas at 1 bar pressure andthe temperature of interest.
Standardization of a solution refers toestablishing the exact concentration ofthe solution, usually through a titration.
A standing wave is a wave motion thatreflects back on itself in such a way thatthe wave contains a certain number ofpoints (nodes) that undergo no motion.A common example is the vibration ofa plucked guitar string, and a relatedexample is the description of electronsas matter waves.
Steel is a term used to describe ironalloys containing from 0 to 1.5% Ctogether with other key elements, suchas V, Cr, Mn, Ni, W, and Mo.
Step-reaction polymerization is a typeof polymerization reaction in whichmonomers are joined together by theelimination of small molecules betweenthem. For example, a moleculemight be eliminated by the reaction ofa H atom from one monomer with an
group from another.
A stereocenter is an asymmetriccarbon atom.
In stereoisomers, the number andtypes of atoms and bonds in moleculesare the same, but certain atoms areoriented differently in space. Cisand trans isomerism is one type ofstereoisomerism; optical isomerism is another.
Stoichiometric coefficients are the coefficients used to balance anequation.
A stoichiometric factor is a conversionfactor relating molar amounts of twospecies in a chemical reaction (i.e., a
¬OH
H2O
1S°2
(g, 1 bar)H2(a = 1)H3O+
Gf° ,
ln K .-RT=¢G°reactant to a product, one reactant toanother, etc.). The numbers used informulating the factor arestoichiometric coefficients.
Stoichiometric proportions refer torelative amounts of reactants that arein the same mole ratio as implied bythe balanced equation for a chemicalreaction. For example, a mixture of 2 mol and 1 mol is in stoichio-metric proportions, and a mixture of 1 mol and 1 mol is not, for thereaction
Stoichiometry refers to quantitativemeasurements and relationshipsinvolving substances and mixtures of chemical interest.
A strong acid is an acid that iscompletely ionized in aqueous solution.
A strong base is a base that iscompletely ionized in aqueous solution.
A strong electrolyte is a substance thatis completely ionized in solution.
A structural formula for a compoundindicates which atoms in a moleculeare bonded together, and whether bysingle, double, or triple bonds.
Structural isomers have the samenumber and kinds of atoms, but theydiffer in their structural formulas.
Sublimation is the passage of moleculesfrom the solid to the gaseous state.
A subshell refers to a collection oforbitals of the same type. For example,the three 2p orbitals constitute the 2psubshell.
A substance has a constantcomposition and propertiesthroughout a given sample and fromone sample to another. All substancesare either elements or compounds.
In a substitution reaction, an atom, anion, or a group in one molecule isreplaced by (substituted with) another.
A substrate is the substance that is acted upon by an enzyme in anenzyme-catalyzed reaction. Thesubstrate is converted to products,and the enzyme is regenerated.
A sugar is a monosaccharide (simple sugar), a disaccharide, or an oligosaccharide containing up to ten monosaccharide units.
The superoxide ion has the structure
.
Superphosphate is a mixture ofand produced by
the action of on phosphate rock.
A supersaturated solution containsmore solute than normally expectedfor a saturated solution, usuallyprepared from a solution that issaturated at one temperature bychanging its temperature to one where supersaturation can occur.
H2SO4
CaSO4Ca(H2PO4)2
O*
O
O2 ¡ 2 H2O.+2 H2
O2H2
O2H2
Surface tension is the energy or workrequired to extend the surface of aliquid.
The surroundings represent thatportion of the universe with whicha system interacts.
A suspension is a heterogeneous fluidcontaining solid particles that aresufficiently large for sedimentationand, unlike colloids, will settle.
Synthesis gas is a mixture of CO(g)and generally made from coalor natural gas, that can be used as afuel or in the synthesis of organiccompounds.
A system is the portion of the universeselected for a thermodynamic study.(See also open, closed, and isolatedsystems.)
A systematic error is one that recursregularly in a series of measurementsbecause of an inherent error in themeasuring system (e.g., through faultycalibration of a measuring device).
Temporary hard water (See hard water.)
A terminal atom is any atom that isbonded to only one other atom in amolecule or polyatomic ion.
A termolecular process is anelementary process in a reactionmechanism in which three atoms ormolecules must collide simultaneously.
A ternary compound is comprised ofthree elements.
A tertiary carbon is attached to threeother carbon atoms.
The tertiary structure of a proteinrefers to its three-dimensionalstructure for example, the twisting and folding of coils.
The theoretical yield is the quantityof product calculated to result from achemical reaction. (See also actualyield and percent yield.)
A theory is a model or conceptualframework with which one is able toexplain and make further predictionsabout natural phenomena.
Thermal energy is energy associatedwith random molecular motion.
The thermite reaction is anoxidation reduction reaction thatuses powdered aluminum metal as areducing agent to reduce a metaloxide, such as to the free metal.
The thermodynamic equilibriumconstant, is an equilibrium constantexpression based on activities. In dilutesolutions activities can be replaced bymolarities and in ideal gases, by partialpressures in atm. The activities of puresolids and liquids are 1.
The third law of thermodynamicsstates that the entropy of a pure perfect
crystal is zero at the absolute zero oftemperature, 0 K.
The titrant is the solution that is addedin a controlled fashion through a buret ina titration reaction. (See also titration.)
Titration is a procedure for carryingout a chemical reaction between twosolutions by the controlled addition(from a buret) of one solution to theother. In a titration a means must befound, as by the use of an indicator,to locate the equivalence point.
A titration curve is a graph of solutionpH versus volume of titrant. It outlineshow pH changes during an acid basetitration, and it can be used to establishsuch features as the equivalence pointof the titration.
A torr is a unit of pressure equal to theunit millimeter of mercury.
The torsional energy is the energydifference between the eclipsed andstaggered forms of ethane.
The term trans is used to describegeometric isomers in which two groupsare attached on opposite sides of adouble bond in an organic molecule, or at opposite corners of a square in asquare-planar complex, or at positionsabove and below the central plane ofan octahedral complex. (See alsogeometric isomerism.)
Transition elements or transitionmetals are those elements whoseatoms feature the filling of a d or subshell of an inner electronic shell. Ifthe filling of an subshell occurs, theelements are sometimes referred to asinner transition elements.
The transition state in a chemicalreaction is an intermediate statebetween the reactants and products. (See also activated complex andreaction profile.)
Triglycerides are esters of glycerol(1,2,3-propanetriol) with long-chainmonocarboxylic (fatty) acids.
In a triple covalent bond, three pairs
of electrons are shared between thebonded atoms. It is represented bya triple-dash sign
A triple point is a condition oftemperature and pressure at which threephases of a substance (usually solid,liquid, and vapor) coexist at equilibrium.
Trouton s rule states that at theirnormal boiling points the entropies ofvaporization of many liquids haveabout the same value:
A unimolecular process is anelementary process in a reactionmechanism in which a single molecule,when sufficiently energetic, dissociates.
A unit cell is a small collection of atoms,ions, or molecules occupying positions
K-1.87 J mol-1
( ).
f
f
in a crystalline lattice. An entire crystalcan be generated by straight-linedisplacements of the unit cell in thethree perpendicular directions.
Unsaturated hydrocarbon moleculescontain one or more carbon-to-carbonmultiple bonds.
An unsaturated solution contains lesssolute than the solvent is capable ofdissolving under the given conditions.
The valence bond method treats acovalent bond in terms of the overlapof pure or hybridized atomic orbitals.Electron probability (or electron chargedensity) is concentrated in the regionof overlap.
Valence electrons are electrons in theelectronic shell of highest principalquantum number, that is, electrons inthe outermost shell.
The valence-shell electron-pairrepulsion (VSEPR) theory is a theoryused to predict probable shapes ofmolecules and polyatomic ions basedon the mutual repulsions of electronpairs found in the valence shell of thecentral atom in the structure.
The van der Waals equation is anequation of state for nonideal gases. Itincludes correction terms to accountfor intermolecular forces of attractionand for the volume occupied by thegas molecules themselves.
The term van der Waals forces is usedto describe, collectively, intermolecularforces of the London type andinteractions between permanent dipoles.
One type of measure of an atomic sizeare van der Waals radii. van der Waalsradii are strictly hard sphere radiimeasured using atomic distances inclosest packed crystals.
Vaporization is the passage ofmolecules from the liquid to thegaseous state.
Vapor pressure is the pressure exertedby a vapor when it is in dynamicequilibrium with its liquid at a fixedtemperature.
A vapor-pressure curve is a graphof vapor pressure as a function oftemperature.
In a vicinal dihalide, a halogen addsacross the double bond of an alkene,and the halogen atoms are bonded toadjacent carbons.
Viscosity refers to a liquid s resistanceto flow. Its magnitude depends onintermolecular forces of attraction andin some cases, on molecular sizes andshapes.
A volt (V) is the SI unit for cell voltage.It is defined as 1 joule per coulomb.
A voltaic (galvanic) cell is anelectrochemical cell in which a
spontaneous chemical reaction produces electricity.
Water gas is a mixture of CO(g) andtogether with some of the
noncombustible gases and produced by passing steam over heated coke.
A wave is a disturbance that transmitsenergy through a medium.
The wavelength is the distancebetween successive crests or troughs ofa wave motion.
Wave mechanics is a form of quantumtheory based on the concepts ofwave particle duality, the Heisenberguncertainty principle, and thetreatment of electrons as matter waves. Mathematical solutions of theequations of wave mechanics areknown as wave functions
Wave particle duality was postulatedby de Broglie and states that at timesparticles of matter have wave-likeproperties and vice versa. This wasdemonstrated in the diffraction patternobserved when electrons were directedat a nickel crystal.
A weak acid is an acid that is onlypartially ionized in aqueous solutionin a reversible reaction.
A weak base is a base that it onlypartially ionized in aqueous solutionin a reversible reaction.
A weak electrolyte is a substance thatis only partially ionized in solution ina reversible reaction.
Work is a form of energy transferbetween a system and its surroundingsthat can be expressed as a force actingthrough a distance.
A zero-order reaction proceeds at arate that is independent of reactantconcentrations. The sum of theconcentration-term exponent(s) inthe rate equation is equal to zero.
The zero-point energy is the lowestpossible energy in a quantummechanical system, such as theparticle-in-a-box energy
corresponding to (page 318).
Zone refining is a purification processin which a rod of material is subjectedto successive melting and freezingcycles. Impurities are swept by amoving molten zone to the end of therod, which is cut off.
A zwitterion is a compound (for example, an amino acid orpolypeptide) containing both acidand base groups. Zwitterions, at neutral pH, typically havesimultaneously positively chargedgroups (cations) and negativelycharge groups (anions).