Transcript
8/8/2019 Chemistry Chapter Summaries
1/23
5
Light is a form of electromagnetic radiation. It wavelength, frequency and
velocity are related by the formula c=v
The electrons in an atom can exist in only certain allowed energy levels
The line spectra o atoms indicate that electrons can transfer from one energy
level to another by the absorption or emission of photons which contain definite
amounts or quanta of energy
An electron in an atom exists in a definite energy level but does not have a
definite location. The region in which an electron moves for most of its time is
called an orbital. Each orbital can hold a maximum of two electrons
The relationship between principle energy level, energy sublevel and orbitals:
Principleenergylevel (n)
Numberof energysublevels(n)
Energysublevels
Numberoforbitalswithineachenergysublevel
Maxelectronpopulation ofenergysublevel
Totnumberoforbitals inprincipleenergylevel (n)
Maxelectronsinprincipleenergylevel(2n)
1 1 s 1 2 1 22 2 s 1 2 4 8
p 3 63 3 s 1 2 9 18
p 3 6d 5 10
4 4 s 1 2 16 32p 3 6d 5 10f 7 14
The arrangement of elements in the periodic table is related to their electron
configurations as follows
Groups I and II (s block) - filling s sublevel
Groups III to VIII (p block) filling p sublevel
Transition elements (d block) filling d sublevel
Lanthanides and actinides (f block) filling f sublevel
The electron configuration of atoms can be represented in several ways, shown
for sodium as follows
2, 8, 1
1s 2s2p6 3s1
Showing electrons in orbitals
8/8/2019 Chemistry Chapter Summaries
2/23
Elements with the same electron configuration in their outer principle energy
level have similar properties
The ionisation energy is the amount of energy required to remove the most
loosely bound electron from a gaseous atom
The first ionisation energy:
1. Increases across a period
2. Decreases down a group
Successive ionisation energies increase for an atom
1. Gradually as the charge on the ion formed increases
2. Markedly when the electron is removed from a lower principle energy level
The valence electrons of an atom are the electrons in the outer principle energy
level
6
Substances are classified into four classes based on their properties
Class Property Melting Point ConductivitySolid Melt
Metallic Variable hardness,malleable
High High High
Ionic Very hard, verybrittle
High None High
CovalentMolecular
Soft brittle solids,can be solids,liquids or gases atroom temperature
Low None None
Covalent Network Very hard, brittle Very high None None
A metal consists of a lattice of positive metallic ions surrounded by a sea of
mobile delocalised valence electrons
Metallic bonding is the electrostatic attraction between the delocalised electrons
and the positive metallic ions
The metallic bonding model can be used to explain the properties of metals
Property ExplanationRelatively high density Ions tightly packed in the latticeMalleable and ductile Metallic bonding is non-directional,
therefore metal lattices can bedeformed without disrupting the
metallic bondingConductivity of electricity and heat Mobile delocalised electrons transfer
8/8/2019 Chemistry Chapter Summaries
3/23
charge and heat energyHigh MP and BP Strong metallic bonding exists
throughout the entire lattice
Ionic substances consist of positive ions and negative ions arranged in a regular
lattice
Ionic bonding is the electrostatic attraction between oppositely charged ions
The ionic bonding model can be used to explain the properties of ionic crystals
Property ExplanationHard and brittle Ions are tightly bound by electrostatic
forces in the crystal lattice. A stressleading tending to distort the crystalcauses repulsion between similarlycharged ions
Non conductivity of electricity whensolid
Ions occupy fixed positions in thelattice
Conductivity of electricity when moltenor in aqueous solution
Mobile ions can transfer electric charge
High MP and BP Ions tightly bound by strongelectrostatic forces
Sodium chloride or common salt is an important ionic compound. Adults need
about 2g of sodium (as Na+) or about 5g of NaCl each day
The noble gas valence electron configuration of eight electrons, called an octet,
is very stable
Ions are formed by the transfer of electrons from an atom of an element of low
ionisation energy to an atom of an element of high ionisation energy
When elements form an ionic compound they achieve a stable octet by gaining
or losing electrons
Electron dot diagrams can be used to show the arrangement of valence electrons
in atoms, molecules and ion
7
Covalent molecular substances include most non-metal elements and most
compound consisting of non-metals only
Within molecules, atoms are held together by the electrostatic attraction
between shared electrons and the nuclei of adjacent atoms. This form of bonding
is called covalent bonding
A single covalent bond is formed when two atoms share a pair of valence energy
level electrons which allows each atom to acquire a noble gas electron
configuration
8/8/2019 Chemistry Chapter Summaries
4/23
A double covalent bond two atoms share two pairs
A coordinate covalent bond is a covalent bond in which one atom provides both
electrons of the shared pair
When atoms combine to form molecules they tend to share electrons so thattheir outer energy level has eight electrons or a noble gas configuration. This is
known as the octet rule. There are exceptions to this rule, especially with
elements which have a higher electron capacity than eight in their valence
energy level (PCl5, SF6, BF3, BeF2, NO, NO2) PNOS B Be
Some compounds contain both ionic and covalent bonds
The shapes of molecules depend on the arrangement in space of the bonding
and non-bonding valence electron pairs of the central atom. The electron pairs
are arranged as far apart as possible to minimise repulsion
Number ofvalence electronpairs
Number ofbonding pairs
Geometry ofmolecule
1 1 Linear2 2 Linear3 3 Triangular planar4 4 Tetrahedral4 3 Pyramidal4 2 Bent4 1 Linear
Electronegativity is a measure of the tendency of an atom to attract electrons
A polar covalent bond is one which there is an uneven charge distribution
between atoms due to unequal attraction of the shared electrons
A polar molecule is one in which there is an uneven charge distribution. The
situation in which there is a separation of positive and negative charge is called
a dipole
To be polar, a molecule must contain one or more polar covalent bonds, and not
be totally symmetrical
When a molecule contains more than one polar bond, the polarity of the
molecule is found by adding vectorially the strength of each of the dipoles
There are three types of attractive forces between molecules which are
collectively known as van der Waals forces
o Dipole-dipole, Dispersion, Hydrogen bonds
Dipole-dipole forces are the forces of attraction between polar molecules
Dispersion forces ate tweak attractive forces existing between all molecules.They arise from the interaction between a temporary dipole and the dipole it
8/8/2019 Chemistry Chapter Summaries
5/23
induces in a neighbouring molecule. In non-polar substances, dispersion forces
are the only intermolecular interactions. The forces are weak but increase with
the number of electrons in a molecule
Hydrogen bonds are bonds between a hydrogen atom attached to an F, N or O
atom in one polar molecule and a non-bonding electron pair on an F, n or O atomin another polar molecule. Hydrogen bonds are stronger than normal dipole-
dipole forces
The properties of covalent molecular substances are:
Property ExplanationLow MP and BP Forces between molecules are weakNon conductors The molecules are uncharged and
electrons are localised in covalentbonds or on the atoms
Generally soft solids Forces between molecules are weak Covalent network substances include non-metal elements such as carbon and
silicon and some non-metal compounds such as silicon carbide and silicon
dioxide
In covalent network substances, every atom is covalently bonded to other atoms
forming a giant network. No separate molecules can be distinguished
The properties of covalent network:
Property Explanation
Very high MP and BP Strong covalent bonding extendingthroughout the lattice
Non-conductors (usually) Electrons localised in covalent bonds oron the atom
Hard and brittle Atoms strongly bound, distortionbreaks covalent bonds
Chemically inert The bonding extends throughout thecrystal and the non-polar nature of thebonding makes them resistant tochemical attack
Insoluble in water and most othersolvents
The strong covalent bonding extendingthroughout the crystal lattice accountsfor the insolubility of these substances
Carbon exists in three allotropic forms-diamond, graphite and buckyballs
8
Mendeleev identified the periodic variation in the properties of the elements
when they are arranged in order of increasing atomic mass
In the modern form of the periodic table, the elements are listed in order of
atomic number and the periodic law states that the properties of the elementsare a periodic function of atomic number
8/8/2019 Chemistry Chapter Summaries
6/23
The trends in the properties:
o Across a period: atomic radius decreases, IE increases, EN increases, non-
metallic character increases
o
Down a group: atomic radius increases, IE decreases, EN decreases,metallic character increases
In general, there is a great variation in properties across a period, whereas in a
group element exhibit more similarities in properties
The group I or alkali metals are very reactive and tend to form +1 ions in the
reactions
o Oxide to form a metal oxide
o
Chlorine to form a metal chloride
o Water to produce hydrogen gas
o Acids explosively to form hydrogen gas
Hydrogen is prepared in the lab by the reaction of a metal with dilute acids
o E.g. Zn + 2HCl ZnCl2 + H2
Hydrogen tends to form covalent molecular compounds when it reacts with other
non-metal elements. It reacts explosively with oxygen to form water. This
reaction is known as the pop test. 2H2 + O2 2H2O
The group II or alkaline earth metals are reactive and tend to form 2+ ions in
their reactions, They undergo similar reactions to the group I elements abut are
generally not as reactive
The group VII elements or halogens are very reactive non-metal which exist as
diatomic molecules. They tend to form -1 ions in their reactions with metals and
covalent molecules in their reactions with non-metals
The group VIII elements or noble gases exist as simple atoms. They are inert
because they have a complete octet in the outer energy level
The elements in which the d energy sublevels are being filled are called the
transition elements
The transition metals are widely used in society because of their useful
properties and relative abundance
o All metals (malleable and ductile, good conductors)
o They have fairly high densities
o They have fairly high MP and BP
8/8/2019 Chemistry Chapter Summaries
7/23
o They are not as reactive as group I and II metals
o They exist in a variety of ionic states
o They commonly form coloured compounds
o They form coordination complexes in with surrounding ligands form
coordinate covalent bond with the central metal ion
The coordination number of a complex ion is the number of coordinate covalent
bonds formed between the central metal ion and surrounding ligands
11
A solution is a homogenous mixture
Different types of solutions occur such as gas in gas, solid in liquid or gas in
liquid, and solid in solid
Solutions are classified:
Saturated Unsaturated SupersaturatedContains as much soluteas the amount of solventcan dissolve at a specifictemperature
Contains less solute thanis needed to saturate it
Contains more solutethan is needed tosaturate it
The solubility of a solute depends on the nature of the solute and solvent. Polarsolvents tend to dissolve polar solutes. Non-polar solvents tend to dissolve
non=polar solutes
Water tends to dissolve polar solutes and many ionic compounds
In aqueous solutions ions are surrounded by polar water molecules
The solubility of solids in liquids usually increases with temperature
The solubility of gases in liquids usually decrease with temperature
The solubility of a gas in a liquid increases with the partial pressure of the gas
above the liquid
An electrolyte is a substance which when dissolved in water produces a
conducting solution
Dissociation is the process by which an ionic crystal separates into ions when it
dissolves
Ionisation occurs when a covalent molecular substance dissolves to form ions
which separate in solution
8/8/2019 Chemistry Chapter Summaries
8/23
Substances are classified as strong, weak or non-electrolytes
o Strong: substances which are essentially completely ionised in solution
o Weak: substances in which only a small fraction of the dissolved molecules
are ionised in solution
o Substances which do not produce ions when dissolve in solution
The conductivity of a solution depends on the strength of the electrolyte, the
solubility of the electrolyte and the concentration of the electrolyte solution
Natural aquatic systems contain dissolved O2, CO2, nitrogen (as NO3- and NH4
+)
and phosphorous (as H2PO4-) which support aquatic life
Environmental problems in aquatic systems include algal blooms, resulting from
high nutrient levels, and salination of soils and waterways
Sea water in a 3.5% solution of ionic compounds and is an important source of
salt for any other substances
Drinking water has added to it chlorine to destroy harmful bacteria and fluoride
to reduce dental decay
Caves are formed when water containing carbon dioxide dissolves limestone
Cave formations develop when a saturated solution of calcium or magnesium
hydrogencarbonate evaporates
Hard water is water which contains high concentrations of salts, particularly the
calcium and magnesium salts of hydrogencarbonate, chloride and sulphate ions
Soaps do not function effectively in hard water as the stearate ion precipitates
out with the Ca and Mg ions. Detergents function in all types of water
Hardness can be removed by:
o Boiling to remove temporary
o Treatment with washing soda (Na2CO3.10H2O)
o Treatment with complex water softeners
o Deionisation with ion exchange resins
o Distillation
Concentrations can be expressed as gL-1, % composition, ppm and mol L-1
The number of moles of solute in a solution is given by the formula n=cV
8/8/2019 Chemistry Chapter Summaries
9/23
When a solution is diluted, the number of moles of the solute remains unchanged
but the concentration decreases
Different calculations involving chemical equations are possible (n=m/M, n=cV,
n=V/22.41)
Precipitation reactions occur when two solutions are mixed and an insoluble solid
is formed
Ionic equations are used for solution reactions to indicate more accurately the
reaction taking place. Spectator ions are not included.
Gravimetric analysis involves using the mass of a precipitate formed in a
precipitation reaction to determine the composition of a substance
Solutions of non-volatile solutes have lower vapour pressures, lower freezing
points and higher boiling points than the pure solvent. The changes in theseproperties depend on the concentration of solute particles in the solution
13
The rate of a chemical reaction is the speed with which reactants are converted
to products
Chemical rations display a great range of reaction rates from very fats, occurring
in a fraction of a second, to very slow, taking place over months or years
The rate of a chemical reaction can be expressed in terms of the rate of removal
of reactants or the appearance of product
Factors which effect the rate of reaction are the nature of the reactants,
concentration or pressure of the reactants, state of sub-division of the reactants,
temperature of the system and the presence of a catalyst
The collision theory of reaction rates is based on the idea that if particle are to
react they must first undergo a collision, For it to be successful and bring about a
change from reactants to products it must have sufficient energy to disrupt thebonds in the reactant molecules, and an orientation that is suitable for the
breaking of some bonds and the formation of others
Activation energy is the minimum energy that must be supplied by the reactant
particles in a chemical reaction if they are to react to form products
An energy profile diagram represents the energy changed which occurs in a
chemical reaction
The transition state or activated complex id the highest energy state in a
chemical reaction. The difference in energy between the reactants and thetransition state is the activation energy for the reaction
8/8/2019 Chemistry Chapter Summaries
10/23
A successful collision is a collision between reactant particles which leads to the
formation of products
A reversible reaction is one in which the formation of products from reactants
and the formation of reactants from products are both significant. A reversible
reaction is represented by double arrows in the chemical equation
The nature of the reactants affects the rate of reactions because different
reactions have different activation energies. Reactions which involve the
breaking of many bonds tend to have higher activation energies and
consequently slower rates
Increasing the concentrations or gas pressures of reactants increases the rate of
collisions and hence the rate of reaction
Increasing the state of subdivisions of solids and liquids in heterogeneous
systems increases the rate of collisions between reactants and hence the rate of
reaction
Increasing the temperature increases the fraction of molecular collisions with
sufficient energy to overcome the activation energy barrier. This leads to an
increased rate of reaction
A catalyst increases the rate by providing an alternative reaction pathway with a
lower activation energy
Catalysts have important roles in the following
o Industrial manufacture of many chemical substances
o The removal of pollutants from combustion processes
o Life sustaining process in plants and animals
14
Chemical equilibrium in a closed system at a constant temperature ischaracterised by the following:
o Constant macroscopic properties, including constant concentrations of
reactants and products
o Equal reaction rates for the forward and reverse reactions
Chemical equilibrium is a dynamic process
Equilibrium exists in physical systems, including the following
o Equilibrium between liquid and vapour in a closed system
8/8/2019 Chemistry Chapter Summaries
11/23
8/8/2019 Chemistry Chapter Summaries
12/23
o Turn litmus red
o Conduct electric current
o Taste sour
o React with reactive metals to produce hydrogen gas
o React with (hydrogen)carbonates to form carbon dioxide
o React with metal (hydr)oxides to form a salt and water
Properties of aqueous solutions of bases:
o Turn litmus blue
o Conduct electric current
o Taste bitter
o React with amphoteric metals to produce hydrogen gas
o React with acids to form salt and water
o Dissolve amphoteric metal hydroxides
Arrhenius theory of acids and bases
o Acid is a substance with produces H+ ions in solution
o Base is a substance which produces OH- ions in solution
Bronsted-Lowry theory of acids and bases
o Acid is a proton donor
o Base is a proton acceptor
o Some substances can react as acids or bases in different reactions
o
Every acid has a conjugate base which is related in the difference of oneproton
o The stronger the acid, the weaker its conjugate base
o Acid-base reactions tend to occur in the direction in which a stronger acid
and stronger base react to form a weaker acid and weaker base
Water is a weak electrolyte which ionises to form H+ and OH- to a small extent
The relationship between the concentrations of H+ and OH- in any aqueous
solution at 25is given by the following: Kw= [H
+
][OH-
] = 1.0
10-14
8/8/2019 Chemistry Chapter Summaries
13/23
The pH of any solution is calculated from: pH= -log10[H+]
The relationship between pH and acidity is 7=neutral, 7 basic
Strong acids and strong bases are essentially completely ionised or dissociated
into ions in aqueous solution
Weak acids and weak bases are those in which only a small proportion of the
molecules are ionised in aqueous solution
Polyprotic acids are those which contain more than one acidic or ionisable
hydrogen per formula unit of the acid
For polyprotic acids successive ionisations occur to successively smaller extents
Some bases contain more than one hydroxide ion per formula unit of the base
A neutralisation reaction is that between an acid and a base
Salts are ionic compounds containing a cation other than H+ and an anion other
than O2- or OH-
Nearly all salts are strong electrolytes
Salt solutions can be acidic, basic or neutral depending on the tendencies of the
ions in the salt to undergo hydrolysis
Carbon dioxide is slightly soluble in water and dissolves to form carbonic acid,
H2CO3. This is a weak diprotic acid which undergoes successive ionisation
reactions to form HCO3- and CO3
2-
Oxides and hydroxides decrease in acidity down groups in the periodic table
16
In volumetric analysis the amount of a particular substance in a sample is
determines by the measurement of the volume of a solution of known
concentration needed to react completely with the substance
A titration is the process in which a solution is added from a burette to another
solution with which it reacts, so that the volume of added solution can be
accurately measured
A volumetric flask is a flask which holds an accurately known volume of solution
A burette is used to deliver an variable but accurately known volume of solution
A primary standard is a substance which has the characteristics:
o Can be obtained in a very pure form
8/8/2019 Chemistry Chapter Summaries
14/23
o Has a known formula
o An be accurately weighed
A standard solution is one whose concentration is accurately known
Standard solutions can be obtained by the following means
o Dissolving known mass of a primary standard to form a definite volume of
solution
o Standardising the solution by titration against a primary standard or a
previously standardised solution
An indicator is a substance which changes colour over a specific pH range
In an acid-base titration:
o The equivalence point is the point at which chemically equivalent amounts
of acid and base have been added. This is when the ratio of moles of acid
and base that have been added is the name as the ole ratio in the
balanced equation
o The end point is the point at which the added indicator changes colour
The pH at the equivalence point in various acid-base titrations:
Type of titration pH at equivalence point Indicator
SA and SB 7 Bromothymol blue,methyl orange,phenolphthalein
SA and WB 5 Methyl orangeWA and SB 9 Phenolphthalein
The preparations, properties and uses of hydrogen chloride, hydrochloric acid,
sulphur dioxide sulphuric acid, and nitric acid are important to note
The important properties of hydrochloric, sulphuric and nitric acids are as follows
o They all strong acids
o They neutralise bases
o Hydrochloric and sulphuric acids produce hydrogen gas with reactive
metals but nitric acid tend s to form nitric oxide
The preparations, properties and uses of sodium hydroxide, sodium carbonate
and ammonia should be known
Sodium hydroxide is a strong base but sodium carbonate and ammonia are
weak. All three neutralise acids
8/8/2019 Chemistry Chapter Summaries
15/23
Sodium hydroxide will dissolve amphoteric metal hydroxides and react with
amphoteric metal to produce hydrogen
Ammonia solution will dissolve metal hydroxides which form complex ions
between the metal ions and ammonia molecules
Fertilisers are added to soils to provide the essential elements needed for plant
growth, including nitrogen, phosphorus, potash and trace elements
Acid rain has a pH
8/8/2019 Chemistry Chapter Summaries
16/23
A redox equation is obtained by adding half-equations which have been
multiplied by factors so the number of electrons is the same in both half-
equations
18
Metals are found as minerals in ores. They are usually in an oxidised form
Metallurgy encompasses the process of mining, milling, extraction and refining.
Metal extraction involves reducing metal compounds to the metal
Two important methods of metal extraction are carbon reduction and electrolytic
reduction
Iron is mined in Australia mainly as hematite (Fe2O3). It is extracted by smeltingin a blast furnace. The reducing agent is carbon monoxide produced from coke.
Limestone is used to remove waste matter as slag
Cast iron, or pig iron, contains up to 5% carbon and is brittle, but forms sharp
casts
Steel is iron with less than 2% iron. It may have other metals alloyed with the
iron for special properties
Gold exists free in nature and combined with sulphur and tellurium. Gold is
extracted using the carbon-in-pulp process
Gold is a relatively inert metal
Chlorine exists in several oxidation states. In nature it ids found as chlorides in
the -1 state. It is prepared in the laboratory by oxidising concentrated
hydrochloric acid with manganese dioxide or potassium permanganate
Chlorine is very reactive. It is a strong oxidising agent and reacts with many
reducing agents including Mg, H2, H2S, SO2 and Fe2+
Chlorine disproportionate in aqueous and basic solutions to form chloride ion andhypochlorite ion. It is used extensively in bleaching and in water purification
Black and white photography utilises the reduction of silver ions in silver halides
on exposure to light
Redox titrations involve the reactions between oxidising agents and reducing
agents. They are frequently used in quantitative analysis
Potassium permanganate is a common oxidising agent. Because it is not a
primary standard, permanganate solution must be standardised before being
used for analysis. The purple colour of the MnO4-
ion makes an indicatorunnecessary in its redox titrations
8/8/2019 Chemistry Chapter Summaries
17/23
Other common oxidising agents used in volumetric analysis are potassium
dichromate and iodine. Common reducing agents include oxalic acids or sodium
oxalate, ammonium iron (II) sulphate and sodium thiosulphate
19
In electrochemical cells stored chemical energy is converted to electrical
energy. A cell generates an emf that depends on the nature of the half-cell
reactions and the concentrations/gas pressures of the reacting substances
In an electrochemical cell, oxidation occurs in one half-cell that is called the
anode. It has the negative terminal. Reduction occurs in the other half-cell, called
the cathode. It has the positive terminal
20
An electrolytic cell operates under an applied emf. Electrical energy is used to
produce chemical change. In this sense electrolytic cells are the reverse of
electrochemical cells
In an electrolytic cell reduction occurs at the cathode and oxidation at the anode.
The cathode is labelled negative and the anode positive
Cations are positive ions which move towards the cathode. Anions are negativeions which move towards the anode
The products of electrolysis in aqueous solutions depend on the following:
relative E0 values of the possible half-reactions, whether inert of reactive
electrodes are used, and the concentration of the reactants
Electrolysis has applications in electro refining, electroplating, extraction of
reactive metals, manufacture of some chemicals, and in anodising
Copper is purified after extraction by electro refining
In the extraction of gold electrolysis is used to reduce the aurocyanide ion to
metallic gold
Electroplating involves the formation of a metal layer on an object used as the
cathode in an electrolytic cell. The plating metal is usually provided as the anode
which gradually dissolves into solution
Alumina is obtained from bauxite by the Bayer process. The mineral gibbsite is
leached using sodium hydroxide, crystallised out as pure Al(OH)2 and
decomposed by heating to produce alumina (Al2O3)
8/8/2019 Chemistry Chapter Summaries
18/23
Aluminium is produced by the electrolytic reduction in the Hall-Heroult process.
Alumina and cryolite are melted and electrolysed. Molten aluminium is liberated
at the cathode. The carbon anodes burn away as gaseous carbon dioxide
Most of the uses of aluminium depend on such properties as its low density, good
conductivity of heat and electricity, resistance to corrosion and good reflectivity
Electrolysis of molten sodium chloride produces sodium and chlorine
Electrolysis of aqueous sodium chloride yields hydrogen, chlorine, and sodium
hydroxide
The quantity of electricity which flows through a circuit is measured in coulombs
and is given by the formula Q=It
The charge on one mole of electrons is 9.65 x 104 C. This is known as Faradays
constant or the faraday. The number of moles of electrons in a given charge iscalculated from the following formula: n(e) = Q/9.65 x 104
The mass of a substance or volume of a gas produced in electrolysis is directly
proportional to the quantity of electricity flowing and inversely proportional to
the number of electrons in the half-equation
When electrolytic cells are connected in series the same electric charge flows
through each cell
21
Organic chemistry and the chemistry of carbon are interchangeable terms which
apply to the study of carbon compounds other than metallic carbonates and
hydrogen carbonates and the oxides of carbon
Carbon is a non-metal element with four valence electrons and an electron
configuration of 2,4 or 1s2 2s22p2
Carbon froes a vast number of different compounds because of its ability to form
chains containing a succession of carbon-carbon bonds
Carbon can form single, double, or triple C-C bonds
The arrangement of atoms around a carbon atom is : four single bonds results in
a tetrahedral shape; one double bond and two single bonds result in a planar
shape, one triple bond and one double bond produce a linear shape
Some rules for bonding carbon-based compounds are: C must form 4 bonds,
halogens must form 1 bond, O must form two bonds, N must form 3 bonds, H
must form 1 bond
8/8/2019 Chemistry Chapter Summaries
19/23
There are a number of ways to represent the structures of organic compounds:
electron dot diagrams, structural formulas, three-dimensional representations
22
Alkanes Alkenes Alkynes
General formula CnH2n+2 CnH2n CnH2n-2
Family name ane ene yne
MP/BP/density All relatively low but increase with increasing
molecular mass
Solubility in water All virtually insoluble
Reaction with
oxygen
Undergo combustion to form carbon dioxide and water
Reactivity Fairly unreactive Very reactive Fairly reactive
Alkyl groups are alkanes from which one hydrogen atom has been removed.
They are named using the stem name of the alkane from which they are
derived
Isomers are different compounds which have the same molecular formula. Thetypes are chain structural: different numbers of C atoms in longest chain;
position structural: functional groups located on different C atoms in chain;
geometric: relative positions of groups attached to C atoms joined by double
bond
Alicyclic hydrocarbons are cyclic hydrocarbons. These can be saturated or
unsaturated and have similar properties to the corresponding aliphatic
hydrocarbons
Aromatic hydrocarbons are those based on the parent compound benzene. The
unique structure of benzene involves the formation of two regions of delocalised
electron charge, containing a total of six electrons, located above and below the
plane of the molecule
Hydrocarbons are very important as fuels as shown by the use of natural gas,
petroleum and coal
Crude oil can be refined by fractional distillation to produce a variety of products
The quality of petrol can be determined from its octane number. This can be
improved by adding branched-chain alkanes, aromatics, some oxygen-containing
organic compounds and tetraethyl lead
8/8/2019 Chemistry Chapter Summaries
20/23
23
Haloalkane
Ether Amine Alcohol Aldehyde Ketone
Carboxylic acid
Ester Amide
RX ROR RNH2 ROH RCHO RCOR
RCOOH RCOOR RCONH2
e.g.fluoro-
-oxy
-ane
-amine -ol -al -one -oic acid -yl
-oate
-amide
Dispersion
Dipole H-H H-H(strong)
Dipole Dipole
H-H(strong)
Dipole H-H
Goodsolvent
fats/oil
Slightly
soluble
Soluble
Soluble Slightlysoluble
Slightly
soluble
Soluble Slightlysoluble
Soluble
Low Higherthanalkanes
Lowerthanalcohols
Relatively high
Higherthanhydrocarbon/haloalkene/ether,but lowerthanalcohol
Asbefore
Relatively high
Lowerthanalcoholsandcarboxylic acids
Similartocarboxylic acids
Haloalkanes can be prepares by halogenations of an alkane
o RH + X2 + UV RX + HX
Hydrohalogenation of an alkene
o RCH=CH2 + HX RCHXCH3
Haloalkanes are fairly unreactive and are used as solvents for non-polar solutes
CFCs are one group of haloalkanes. They have been linked to ozone depletion
There are three classes of alcohols called primary, secondary and tertiary,
depending on how many alkyl groups are attached to the carbon atom to which
the OH group is attached
Alcohols can be prepared by the hydration of an alkene
o RCH=CH2 + H2O + H+RCHOHCH3
Alcohols can react with sodium to form sodium alkoxides and hydrogen
o 2ROH + 2Na 2RO-Na+ + H2
Different alcohols form different products when treated with oxidising agents
primary form aldehydes, which form carboxylic acids. Secondary oxidise to form
ketones.
8/8/2019 Chemistry Chapter Summaries
21/23
Alcohols react with carboxylic acids to form esters
o RCOOH + ROH RCOOR + H2O
Methanol is the simplest alcohol, a good solvent, and very poisonous
Ethanol is the alcohol in drinks, produced by the fermentation of glucose
(C6H12O6)
Ethanol is produced industrially by the hydration of ethene in acidic conditions
Aldehydes can be prepared by oxidising primary alcohols
o RCH2OH RCHO + 2H+ + 2e-
Aldehydes can be further oxidised to carboxylic acids
o RCHO + H2O RCOOH + 2H+ + 2e-
Ketones can be prepared by oxidising secondary alcohols
o RCHOHR RCOR + 2H+ + 2e-
Ketones cannot be oxidised
Carboxylic acids are produced by the oxidation of primary alcohols and aldehyes
Carboxylic acids are weak acids; react with metals to form hydrogen gas; and
neutralise base
The strength of the acid depends on the length of the hydrocarbon chain and the
electro-negativities of any functional groups attached to the hydrocarbon chain
(e.g. Cl)
Carboxylic acids react with alcohols to form esters
o RCOOH + ROH (+H+) RCOOR + H2O
Fatty acids are long chain aliphatic carboxylic acids which are found in natural
esters in fats and oils. They can be saturated or unsaturated hydrocarbon chains
Esters are formed by the reaction of an alcohol and a carboxylic acid in the
presence of a strong acid like sulphuric acid
Esters can be hydrolysed in acid and alkaline conditions, giving different
products
Fats and oils are natural esters known as triglycerides. They are formed by the
reaction of 1,2,3-propanetriol, or glycerol, with fatty acids
8/8/2019 Chemistry Chapter Summaries
22/23
24
Saponification is the soap making process in which an oil or fat is treated with
NaOH or KOH solution
Soaps are the sodium or potassium salts of fatty acids
Detergents are the salts of alkyl-benzene sulfonates
Soaps and detergents function as cleaning agents because the charged end of
the surfactant ion dissolves in the polar solvent water while the non-polar
hydrocarbon chain dissolves in the non-polar grease, oil or dirt
Soaps do not function effectively in hard water as the surfactant ion precipitates
out with the Ca2+ and Mg2+ ions. Detergents function in all types of water
Polymers are large molecules made up by bonding together small repeatingmolecules called monomers
There are two types of polymerisation processes, addition and condensation
Addition: small molecules with a C=C double bond join together, with a catalyst
Condensation: two monomers link together with the accompanying elimination
of a molecule of water. Often one monomer is a dicarboxylic acid and the other a
diamine or diol
Thermoplastics are polymers which can be softened by heating
8/8/2019 Chemistry Chapter Summaries
23/23
Thermosetting plastics cannot be softened by heating after their initial shaping
and setting
Elastomers are polymers that can be stretched but return to their original shape
when the distorting force is removed
The structural formula of an unknown organic compound can be determined by
i. Determine qualitative composition (experimentally)
ii. Determine quantitative composition (experimentally)
iii. Calculate EF
iv. Determine relative molecular mass (experimentally)
v. Calculate molecular formula
vi. Determine structural formula
Reference:
All notes taken from:
J.D.Anderson, P.J.Garnett, W.R.Liddelow, R.K.Lowe, I.J.Manno. Foundations of Chemistry.
2nd ed. Melbourne: Pearson Education Australia; 1996.
top related