Ch 3 chapter 3 Lecture Notes

7/22/2019 Ch 3 chapter 3 Lecture Notes

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CHM 1045 Notes

Dr. Palmer Graves

Chapter 3

1

Chapter 3Molecules,

Compounds,

and Chemical

Equations

3.1 Define and distinguish

between ionic and covalent bonds

and represent molecules with

formulas. [Readings 3.2-3.4

Problems 23-32]

Elements and Compounds

elements combine together to make an almost

limitless number of compounds

the properties of the compound are totally

different from the constituent elements


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Chapter 3

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Formation of Water from Its Elements

Chemical Bonds compounds are made of atoms held together by

chemical bonds

bonds are forces of attraction between atoms

the bonding attraction comes from attractions

between protons and electrons

Covalent Bonds: Molecules

Molecules result from a chemical bond between

two or more atoms

Covalent Bonds form when two atoms share

electrons

Example: H2O, CO2, C6H12O6


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Bond Types two types of bonding - ionic and covalent

ionic bonds electrons have been transferred between atoms oppositely charged ions that attract each other

metal atoms bonded to nonmetal atoms

covalent bondsresult when two atoms share some of their

electrons

nonmetal atoms bonded to nonmetal atoms

Formation of Ionic Compound

2 Na(s) + Cl2(g) 2 NaCl(s)

Na+ions and Cl-ions are formed by the trans-

fer of an electron from a Na atom to a chlorine

atom of Cl2. The resulting ions arrange them-selves in a 3D array of alternating charged ions.

Click on pictures to view movies.

Formation of Molecular Compound

P4(s) + 6 Cl2(g) 4 PCl3(l)

Discrete molecules of phosphorous trichloride,

PCl3, are formed by reacting solid phorphorous

with chlorine gas.

Click on pictures to view movies.


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Chapter 3

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Molecular and Ionic Compounds

Molecular compounds - fundamental particles

are discrete molecules such a water, H2O

Ionic compounds - fundamental particles are

ions arranged in 3D array such as shown for

sodium chloride, NaCl

Copyright 2000 John Wiley and Sons, Inc.

Formula Types

Name Chemical Formula Structural Formula

methane - CH4

ethane C2H6 CH3 CH3

propane C3H8 CH3 CH2 CH3 Structural Formula Ball and Stick

Types of Formula

Empirical Formula

Empirical Formuladescribe the kinds of

elements found in the compound and the

ratio of their atoms

they do not describe how many atoms, the orderof attachment, or the shape

the formulas for ionic compounds are empirical


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Types of Formula

Molecular Formula

Molecular Formuladescribe the kinds of

elements found in the compound and the

numbers of their atoms

they do not describe the order of attachment, or

the shape

Types of Formula

Structural Formula

Structural Formula

elements found in the compound

the numbers of their atoms

order of atom attachment

type of attachment

use lines to represent covalent bonds

each line describes the number of electrons shared bythe bonded atoms

single line = single covalent bond

double line = double covalent bond

triple line = triple covalent bond

Representing Compounds

Molecular Models

Modelsshow the 3-dimensional structure

Ball-and-Stick Modelsuse balls to represent

the atoms and sticks to represent the

attachments between them Space-Filling Modelsshow the electron clouds


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Chemical Formulas

Hydrogen Peroxide

Molecular Formula = H2O2Empirical Formula = HO

Benzene

Molecular Formula = C6H6Empirical Formula = CH

Glucose

Molecular Formula = C6H12O6Empirical Formula = CH2O

Types of Formula

Tro, Chemistry: A Molecular

Approach

18

Molecular View of

Elements and Compounds


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Classifying Materials

atomic elements = particles are single

atoms

molecular elements = particles are

multi-atom molecules

molecular compounds = particles are

molecules made of only nonmetals

ionic compounds = particles are

cations and anions

Molecular Elements Certain elements occur as 2 atom molecules

Rule of 7s

Other elements occur as polyatomic molecules

P4, S8, Se8

H2

Cl2

Br2

I2

7

7A

N2 O2 F2

Molecular Elements


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Chapter 3

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3.2 Write the formula and name

for ionic compounds [Readings

3.5 Problems 33-48]

Ionic Compounds

metals + nonmetals

no individual molecule units, instead

have a 3-dimensional array of cations

and anions made of formula units

many contain polyatomic ions

several atoms attached together in one ion

Ionic Compounds Ionic compounds are

formed from positive

and negative ions

Subscripts are used to

indicate an electricallyneutral formula unit

Use the smallest

whole number set


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Compounds that Contain Ions

if Na+is combined with S2-, you will need 2 Na+

ions for every S2-ion to balance the charges,therefore the formula must be Na2S

Writing Formulas for

Ionic Compounds

1. Write the symbol for the metal cation and its charge

2. Write the symbol for the nonmetal anion and its charge

3. Charge (without sign) becomes subscript for other ion

4. Reduce subscripts to smallest whole number ratio

5. Check that the sum of the charges of the cation cancels the sum of

the anions

Write the formula of a compound made from

aluminum ions and oxide ions

1. Write the symbol for the metal cation

and its charge

2. Write the symbol for the nonmetal

anion and its charge

3. Charge (without sign) becomes

subscript for other ion

4. Reduce subscripts to smallest whole

number ratio

5. Check that the total charge of the

cations cancels the total charge of the

anions


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Practice - What are the formulas for

compounds made from the following ions?

potassium ion with a nitride ion

calcium ion with a bromide ion

aluminum ion with a sulfide ion

Naming Ionic Compounds

Binary Ionic Compounds

Cation name is first e.g. Na+is sodium

Anion is named second

The stem is used followed by ide

e.g. O 2-is called oxide

S2-is sulphide

Na2O is called sodium oxide

Sodium chloride

Barium chloride

Metal Cations

Type I Metals with Invariant

Charge

metals whose ions can only have

one possible charge

Groups 1A+1& 2A+2, Al+3, Ag+1,

Zn+2, Sc+3

cation name = metal name

Type II Metals with

Variable

Charges! metals whose ions can

have more than one

possible charge! determine charge by

charge on anion

! cation name = metal

name with Roman

numeral charge in

parentheses


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Chapter 3

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Ionic Compounds

Distinguish between Type I vs.

Type II metals

Type I ionic compound names

include the cation and anion

only

Type I Metals

Naming Binary Ionic Compounds for

Type I Metals (Invariant Charge) Contain Metal Cation + Nonmetal Anion

Metal listed first in formula and name

1. name metal cation first, name nonmetal anionsecond

2. cation name is the metal name

3. nonmetal anion named by changing the endingon the nonmetal name to -ide

Example Naming Binary Ionic

with Invariant Charge Metal

CsF1. Identify cation and anion

2. Name the cation

3. Name the anion

4. Write the cation name first, then the anion name


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Name the following compounds

1. KCl

2. MgBr2

3. Al2S3

Naming Binary Ionic Compounds for

Type II Metals (Variable Charge) Contain Metal Cation + Nonmetal Anion

Metal listed first in formula and name

1. name metal cation first, name nonmetal anionsecond

2. metal cation name is the metal name followed bya Roman numeral in parentheses to indicate itscharge

determine charge from anion charge

common ions Table 3.4

3. nonmetal anion named by changing the ending onthe nonmetal name to -ide

Determining the Charge on a Cation

with Variable Charge Au2S3!" determine the charge on the anion

Au2S3- the anion is S, since it is in Group 6A, its charge is -2

#" determine the total negative charge

since there are 3 S in the formula, the total negative charge is -6

$" determine the total positive charge

since the total negative charge is -6, the total positive charge is +6

%" divide by the number of cationssince there are 2 Au in the formula and the total positive charge is+6, each Au has a +3 charge


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Chapter 3

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Example Naming Binary Ionic

with Variable Charge Metal

CuF2

1. Identify cation and anion

2. Name the cation

3. Name the anion

4. Write the cation name first, then the anion name

Name the following compounds

1. TiCl4

2. PbBr2

3. Fe2S3

Example Writing Formula for Binary Ionic

Compounds Containing Variable Charge Metal

manganese(IV) sulfide

1. Write the symbol for the cation and its

charge

2. Write the symbol for the anion and its

charge




number ratio



anions

-


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1. copper(II) ion with a nitride ion

2. iron(III) ion with a bromide ion

Compounds Containing

Polyatomic Ions

Polyatomic ions are single ions that containmore than one atom

Often identified by (ion) in formula

Name and charge of polyatomic ion do not change

Name any ionic compound by naming cation first andthen anion

Some Common Polyatomic Ions

NH4+ammonium

Cr2O72dichromate

CrO42chromate

NO2nitrite

NO3nitrate

OHhydroxide

HCO3hydrogen carbonate

(aka bicarbonate)

CO32carbonate

C2H3O2acetate

FormulaName

HSO3hydrogen sulfite

(aka bisulfite)

HSO4hydrogen sulfate

(aka bisulfate)

SO32sulfite

SO42sulfate

ClO4perchlorate

ClO3chlorate

ClO2chlorite

ClOhypochlorite

FormulaName


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Chapter 3

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Patterns for Polyatomic Ions

!" elements in the same column form similarpolyatomic ions

same number of Os and same charge

ClO3- = chlorate "BrO3

-= bromate

#" if the polyatomic ion starts with H, addhydrogen- prefix before name and add 1 to thecharge

CO32-= carbonate"HCO3

-1= hydrogen carbonate

Periodic Pattern of Polyatomic Ions

-ate groups

BO3-3

NO3-1

SiO3-2

PO4-3

SO4-2

ClO3-1

AsO4-3

SeO4-2

BrO3-1

TeO4-2

IO3-1

CO3-2

3A 4A 5A 6A 7A

Patterns for Polyatomic Ions -ate ion

chlorate = ClO3-1

-ate ion + 1 O#same charge,per-prefix

perchlorate = ClO4-1

-ate ion 1 O#same charge, -itesuffix chlorite = ClO2

-1

-ite ion 1 O#same charge, hypo-prefix,

-itesuffix

hypochlorite = ClO-1


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Polyatomic Ions

SO42-

SO32-

NO3

NO2

ClO3

ClO2

ClO

ClO4

1. Identify the ions

2. Name the cation

3. Name the anion

4. Write the name of the cation followed by thename of the anion

Example Naming Ionic Compounds

Containing a Polyatomic Ion

Na2SO4

Example Naming Ionic Compounds

Containing a Polyatomic Ion

Fe(NO3)31. Identify the ions

2. Name the cation

3. Name the anion

4. Write the name of the cation followed bythe name of the anion


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Name the following

1. NH4Cl

2. Ca(C2H3O2)2

3. Cu(NO3)2

Example Writing Formula for Ionic

Compounds Containing Polyatomic Ion

Iron(III) phosphate


charge


charge




number ratio



anions



1. aluminum ion with a sulfate ion

2. chromium(II) with hydrogen carbonate


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Hydrates hydrates are ionic compounds containing a

specific number of waters for each formula

unit water of hydration often driven off byheating

in formula, attached waters follow CoCl26H2O

in name attached waters indicated by suffix-hydrateafter name of ionic compound CoCl26H2O = cobalt(II) chloride hexahydrate

CaSO4!H2O = calcium sulfate hemihydrate

8octa

7hepta

6hexa

5penta

4tetra

3tri

2di

1mono

!hemi

No. of

Waters

Prefix

Hydrate

CoCl26H2O

Anhydrous

CoCl2

Practice

1. What is the formula of magnesium sulfate

heptahydrate?

2. What is the name of NiCl26H2O?

3.3 Write the formula and name

for molecular compounds

[Readings 3.5 Problems 49-64]


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Chapter 3

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Tro, Chemistry: A Molecular

Approach

55

Writing Names of Binary Molecular

Compounds of 2 Nonmetals1. Write name of first element in formula

element furthest left and down on the Periodic Table use the full name of the element

2. Writes name the second element in the formula withan -idesuffix

as if it were an anion, however, remember thesecompounds do not contain ions!

3. Use a prefix in front of each name to indicate thenumber of atoms

a) Never use the prefix mono-on the first element

Subscript - Prefixes

1 = mono-

not used on first nonmetal

2 = di-

3 = tri-

4 = tetra-

5 = penta-

6 = hexa-

7 = hepta-

8 = octa-

9 = nona-

10 = deca-

drop last a if name begins with vowel

Example Naming Binary Molecular

BF31. Name the first element

2. Name the second element with anide

3. Add a prefix to each name to indicate the subscript

4. Write the first element with prefix, then the second elementwith prefix

Drop prefix monofrom first element


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Chapter 3

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Name the following

1. NO2

2. PCl5

3. I2F7

Example Binary Molecular

dinitrogen pentoxide

Identify the symbols of the elements

nitrogen = N

oxide = oxygen = O

Write the formula using prefix number for

subscript

di = 2, penta = 5

N2O5

Write formulas for the following

1. dinitrogen tetroxide

2. sulfur hexafluoride

3. diarsenic trisulfide


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Acids acids are molecular compounds that form H+

when dissolved in water to indicate the compound is dissolved in water (aq)

is written after the formula

not named as acid if not dissolved in water

sour taste

dissolve many metals

like Zn, Fe, Mg; but not Au, Ag, Pt

formula generally starts with H

e.g., HCl, H2SO4

Acids Contain H+1cation and

anion

in aqueous solution

Binary acids have H+1

cation and nonmetalanion

Oxyacids have H+1

cation and polyatomicanion

Naming Binary Acids

write a hydroprefix

follow with the nonmetal name

change ending on nonmetal name toic

write the word acidat the end of the name


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Example - Naming Binary

Acids HCl(aq)

1. Identify the anion

2. Name the anion with an ic suffix

3. Add a hydro-prefix to the anion name

4. Add the word acidto the end

Naming Oxyacids

if polyatomic ion name ends in ate, then

change ending toic suffix

if polyatomic ion name ends in ite, then

change ending to ous suffix

write word acid at end of all names

Example Naming Oxyacids

H2SO4(aq)


2. If the anion has atesuffix, change it to ic. If

the anion has itesuffix, change it to -ous

3. Write the name of the anion followed by the

word acid


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Example Naming Oxyacids

H2SO3(aq)


2. If the anion has atesuffix, change it to ic. If theanion has itesuffix, change it to -ous

3. Write the name of the anion followed by the word acid

Name the following

1. H2S

2. HClO3

3. HNO2

Writing Formulas for Acids

when name ends in acid, formulas starts with H

write formulas as if ionic, even though it ismolecular

hydro prefix means it is binary acid, no prefixmeans it is an oxyacid

for oxyacid, if ending isic, polyatomic ion endsinate; if ending isous, polyatomic ion ends inous


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Example Binary Acids

hydrosulfuric acid

1. Write the symbol for the cation and itscharge


charge



4. Add (aq) to indicate dissolved in

water



anions

Example Oxyacids

carbonic acid


charge


charge



4. Add (aq) to indicate dissolved in

water



anions

Example Oxyacids

sulfurous acid

1. Write the symbol for thecation and its charge

2. Write the symbol for theanion and its charge

3. Charge (without sign)

becomes subscript forother ion

4. Add (aq) to indicatedissolved in water

5. Check that the total chargeof the cations cancels thetotal charge of the anions


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Chapter 3

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Practice - What are the formulas for the

following acids?

1. chlorous acid

2. phosphoric acid

3. hydrobromic acid

3.4 Calculate mass percent of an

element in a compound. Use

mass percent as a conversion

factor. [Reading 3.8 Problems

65-73]

Formula Mass

the mass of an individual molecule orformula unit

The mass is taken from the Periodic Table

also known as molecular mass or molecular

weight Add the masses of the atoms in a single

molecule or formula unit

mass of 1 molecule of H2O

= 2(1.01 amu H) + 16.00 amu O = 18.02 amu


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Molar Mass of Compounds the relative masses of molecules can be calculated

from atomic massesFormula Mass = 1 molecule of H2O

= 2(1.01 amu H) + 16.00 amu O = 18.02 amu

since 1 mole of H2O contains 2 moles of H and 1mole of O

Molar Mass = 1 mole H2O

= 2(1.01 g H) + 16.00 g O = 18.02 g

so the Molar Mass of H2O is 18.02 g/mole

Example Find the number of CO2molecules

in 10.8 g of dry ice

1 mol CO2= 44.01 g,

1 mol = 6.022 x 1023

10.8 g CO2molecules CO2

Check:

Solution:

Concept Plan:

Relationships:

Given:

Find:

g CO2 mol CO2 molec CO2

Practice - Converting Grams to Molecules

How many molecules are in 50.0 g of PbO2?

(PbO2= 239.2)


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Percent Composition Percentage of each element in a compound

By mass Can be determined from

1. the formula of the compound

2. the experimental mass analysis of the compound

The percentages may not always total to 100% due torounding

Example 3.13 Find the mass percent of

Cl in C2Cl4F2

C2Cl4F2% Cl by mass

Check:

Solution:

Concept Plan:

Relationships:

Given:

Find:

Practice - Determine the Mass Percent

Composition of the following

CaCl2(Ca = 40.08, Cl = 35.45)


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Mass Percent as a

Conversion Factor

the mass percent - mass of a constituent

element in 100 g of the compound

CCl2F2is 58.64% Cl by mass thus, 100 g of

CCl2F2contains 58.64 g Cl

this can be used as a conversion factor

100 g CCl2F2: 58.64 g Cl

Example 3.14 Find the mass of table

salt containing 2.4 g of Na

since the mass of NaCl is more than 2x the mass of

Na, the number makes sense

100. g NaCl : 39 g Na

2.4 g Na, 39% Na

g NaCl

Check:

Solution:

Concept Plan:

Relationships:

Given:

Find:

g Na g NaCl

Practice Benzaldehyde is 79.2% carbon. What

mass of benzaldehyde contains 19.8 g of C?


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3.5 Calculate and relate moles,

grams, and number of molecules

in a compound. [Reading 3.8

Problems 75-78]

Conversion Factors in Chemical

Formulas

chemical formulas show the numbers of atoms

and molecules

or moles of atoms and moles of molecules

these relationships can be used as conversion

factors between amounts of constituent elements

and molecules

like percent composition

Example 3.15 Find the mass of hydrogen in

1.00 gal of water

since 1 gallon weighs about 3800 g, and H is light,

the number makes sense

3.785 L = 1 gal, 1 L = 1000 mL, 1.00 g H 2O = 1 mL,

1 mol H2O = 18.02 g, 1 mol H = 1.008 g, 2 mol H : 1 mol H 2O

1.00 gal H2O, dH2O= 1.00 g/ml

g H

Check:

Solution:

Concept Plan:

Relationships:

Given:

Find:

gal H2O L H2O mL H2O g H2O

g H2O mol H2O moL H g H


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Practice - How many grams of sodium are in 6.2 g

of NaCl? (Na = 22.99; Cl = 35.45)

3.6 Calculate the empirical

formula from experimental data.

[Reading 3.9 Problems 79-84]

Empirical Formula

simplest, whole-number ratio of the atoms

of elements in a compound

can be determined from elemental analysis

masses of elements formed when decompose or

react compound

combustion analysis

percent composition


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Finding an Empirical Formula1) Percentage is the number of grams in 100 grams of

compound

a) assume you start with 100 g of the compound

2) convert grams to molesa) use molar mass of each element

3) write a pseudoformula using moles as subscripts

4) divide all by smallest number of moles"# if result is within 0.1 of whole number, round to whole

number

5) multiply all mole ratios by number to make allwhole numbers

a) if ratio ?.5, multiply all by 2; if ratio ?.33 or ?.67, multiplyall by 3; if ratio 0.25 or 0.75, multiply all by 4; etc.

b) skip if already whole numbers

Example 3.17

Laboratory analysis of aspirin determined

the following mass percent composition.

Find the empirical formula.

C = 60.00%

H = 4.48%

O = 35.53%

Example:

Find the empirical formula

of aspirin with the given

mass percent composition.


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Write a Concept Plan:

g

C, H, O

mol

C, H, O

mol

ratio

empirical

formula

Example:

Find the empirical

formula of aspirin with

the given mass percent

composition.

Information

Given: 60.00 g C, 4.48 g H, 35.53 g O

Find: Empirical Formula, CxH

yO

z

Example:

Find the empirical

formula of aspirin with

the given mass percent

composition.

Information

Given: 60.00 g C, 4.48 g H, 35.53 g O

Find: Empirical Formula, CxH

yO

z

CP: g C,H,O!mol C,H,O!

mol ratio!empirical formula

3.7 Given the empirical formula

and the molecular weight,

calculate the molecular weight.[Reading 3.9 Problems 85-90]


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Molecular Formulas

The molecular formula is a multiple of the

empirical formula

To determine the molecular formula you

need to know the empirical formula and

the molar mass of the compound

Example 3.18 Find the molecular

formula of butanedioneemp. form. = C2H3O;

MM = 86.03 g/mol

molecular formula

Check:

Solution:

Concept Plan:

and

Relationships:

Given:

Find:

Practice Benzopyrene has a molar mass of

252 g/mol and an empirical formula of C5H3. What

is its molecular formula? (C = 12.01, H=1.01)


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Practice with the Concept

Ibuprofen is found to contain 75.69% C;

15.51 % O; and 8.80% H by mass. What is

the empirical formula of Ibuprofen?

3.8 Write and balance chemical

equations. [Reading 3.10

Problems 91-100]

Chemical Equations

A chemical equation

relates what we see

with what is going on

at the molecular level

A balanced chemical

equation describes

symbolically a

chemical reaction, or a

molecular event


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Chemical Equations

An equation is balanced when all of thereactant atoms are also present in theproducts

Formation of water reacts hydrogen andoxygen gas

Both hydrogen and oxygen are diatomic

H2(g) + O2 (g)! H2O (g)

Is the reaction balanced?

Chemical Equations

A chemical equation represents a chemical reaction:

Before ! After Reactants ! Products Atoms in Before ! Atoms in After

Arrangement Arrangement

Conservation of atoms: there are the same number and

kind of atoms after a chemical reaction as before the

reaction.

Since atoms have a consistent weight: mass is also

conserved.

Chemical Equations

Balancing Chemical Equations

Step 1: Write the unbalanced equation.Make sure that each formula is written

correctly. Step 2: Adjust the coefficients to get equal

numbers of each kind of atom on both sidesof the arrow.

Reduce to the smallest whole number ratio


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Chemical Equations

Tips

1. Balance for elements other than O and Hfirst.

2. Balance polyatomic ions as a group ifpossible

3. When elements appear in the equationseparately, balance them separately.

The process is TRIAL AND ERROR!!

Balancing Equations

This precipitation

reaction is between

lead(II) nitrate and

potassium iodide

The reaction is similar

to one between

cobalt(II) nitrate and

sodium phosphate

Write the equation

Balancing Equations

From a reaction

Conservation of Atoms: How? Adjust coefficients.

Method: systematic trial and error.


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Examples

__S8+ __O2!__SO2__Pb(NO3)2+__K2CrO4!__PbCrO4+__KNO3__Cu +__HNO3!__NO2+__Cu(NO3)2+__H2O

Rules for Balanced Equations

Same number and kind of atoms on both sides.

Same overall net electrical charge.

Cannot change the subscripts of compounds:

Only change the coefficients.

Coefficients should be the lowest ratio integers.

Mathematically they are similar to algebraic

equations.

3.9 Write the names and formulas

for simple organic compounds as

well as organic functional groups.

[Reading 3.10 Problems 101-

108]


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Organic vs. Inorganic Compounds

the main element that is the focus of organicchemistry is carbon

organic compounds contain C and H,sometimes with O, N, P, S, and traceamounts of other elements

organic compounds are found in livingorganisms and are produced in the lab

Carbon Bonding

carbon atoms bond almost exclusively covalently

Carbon forms 4 covalent bonds

4 single bonds, 2 double bonds, 1 triple + 1 single, etc.

carbon is unique in that it can form limitless

chains of C atoms, both straight and branched, and

rings of C atoms

Carbon Bonding


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Classifying Organic Compounds

two main categories oforganic compounds

hydrocarbonsandfunctionalizedhydrocarbons

hydrocarbons containonly C and H

most fuels are mixtures ofhydrocarbons

Classifying Hydrocarbons

hydrocarbons containing only single bonds

are called alkanes

hydrocarbons containing one or more C=C

are called alkenes

hydrocarbons containing one or more C$C

are called alkynes

hydrocarbons containing C6benzene ring

are called aromatic

Naming Straight Chain Hydrocarbons

consists of a base name to indicate the number of

carbons in the chain, with a suffix to indicate the

class and position of multiple bonds

suffix ane for alkane, ene for alkene, yne for alkyne

10dec-5pent-

9non-4but-

8oct-3prop-

7hept-2eth-

6hex-1meth-No. of CBase NameNo. of CBase Name


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CHM 1045 Notes

Dr. Palmer Graves

Chapter 3

Functionalized Hydrocarbons

functional groupsgenerally give a group

of molecules common properties

functional groups - usually replace Hs on a

hydrocarbon chain

generally, the chemical reactions of the

compound are determined by the kinds of

functional groups on the molecule

Functional Groups

Ch 3 chapter 3 Lecture Notes

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