Chem Summmary

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CHEMISTRY SUMMARY

1 EQUILIBRIA

Chemical Equilibria

Reversible reactions, dynamic equilibrium.

(a) Factors affecting chemical equilibria: Le Chateliers principle.


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The following examples are useful: (i) the hydrolysis of simple esters, (ii)

the synthesis of ammonia, (iii) acid base behaviour.(b) Equilibrium constants, their definition and their calculation in terms of

concentrations. The qualitative effect of temperature on equilibrium

constants.

The concentration of solids and pure liquids are not included in the

expression for the equilibrium constant.

Careful distinction should be drawn between those cases where a change in

the composition of the equilibrium mixture occurs (i) with the constant

unchanged, e.g. in response to a change in concentration, (ii) because of

change in the value of the equilibrium constant, in response to a change in

temperature.

1.2 Ionic Equilibria(a) Bronsted-Lowry theory of acids and bases. Qualitative distinction

between strong and weak acids in terms of conductivity.


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An appreciation that strong electrolytes, in contrast to weak electrolytes, are

effectively fully dissociated in all but the most concentrated solutions is

expected. Definition and details of the measurement of any form of

conductivity are not required.

Degree of dissociation a, described in terms of actual concentration of

hydrogen (or hydroxide) ion relative to maximum theoretical concentration.

No treatment of pKa,Kb or pKb is required.

(b) The ionic product of waterKw.

(c) pH.Calculation of pH from concentration for strong acids and from

concentration and Ka for weak acids using Ka = a2/V (derivation not

required).

pH indicators: choice of indicators.

(d) Buffer solutions a qualitative treatment only. Reference should be

made to the importance of buffers in biological systems.

1.3 Chromatography

Treated as an equilibrium between a stationary and a moving phase.

Practical experience should be given in paper, thin layer and column

chromatography. The use of R1 values. Gas chromatography, the use of

peak heights and retention times. The widespread application of these

methods in industry and medicine should be noted.

2 REACTION KINETICS


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(a) Simple rate equations; order of reaction; rate constants.

Rate = k[A]n[B]m.

Treatment should be limited to simple cases of single step reactions and of

multi-step processes with a rate-determining step, for which n and m are

both integral and are either 0, 1 or 2. The use of the integrated forms of first-

and second-order rate equations is not required but the use of constancy of

half-life as a test for first order kinetics is included.

Simple calculations on half-life may be set. Questions will not be set

requiring candidates to determine the order of a reaction using methods thatinvolve drawing tangents to curves. Candidates will not be asked to

determine the values of rate constants but should be able to construct a rate

equation for a reaction by inspection of suitable data.

The use of order of reaction in checking that a given reaction mechanism is

consistent with the observed kinetics.

(b) The qualitative effect of temperature on rate constants; concept of

activation energy as an energy barrier.


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Interpreted qualitatively in terms of the variation with temperature of the

Boltzmann distribution.

(c) Catalysis

It should be appreciated that in the presence of a catalyst a reaction follows

an alternative path, i.e. a different barrier of lower energy is involved.


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3 THERMOCHEMISTRY AND CHEMICAL ENERGETICS

(a)


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(b) Lattice energies for simple ionic crystals. A qualitative appreciation of

the effects of ionic charge and ionic radius on the magnitude of a lattice

energy. A treatment of the Born-Haber cycle is not required.

4 THE PERIODIC TABLE: PRINCIPLES OF CHEMICAL PERIODICITY

4.1 Periodicity of Physical Properties


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A qualitative appreciation of the variation in physical properties with atomic

number across the second and third periods (lithium to neon, sodium to

argon).

The variation in first ionisation energies, atomic radii, melting points.

Interpretation and explanation or the above trends and gradations in terms of

structure and bonding of the elements.

Ionic Bonds


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Example of covalent bond

4.2 Periodic Patterns in the Chemical Properties of Compounds

Study in this sub-section should be restricted to the oxides, chlorides andsimple hydrides (also excluding 'MgH2' and 'AIH3') of the elements sodium

to chlorine.


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The patterns and gradations in properties should be interpreted in terms of

key atomic and electronic factors such as atomic and ionic radii, ionisation

energies and electronegativities.

(a) Variation in oxidation number illustrated by the oxides, chlorides and

simple hydrides.

(b) (i) Reaction of oxides, chlorides and simple hydrides with water.

(ii) Acid/base behaviour of oxides.

No treatment of peroxides or superoxides is required.

5 A STUDY OF THE ELEMENTS IN SOME GROUPS OF THE

PERIODIC TABLE

5.1 Group II

The elements magnesium, calcium, strontium and barium.

A group of reactive metals which are essentially similar to each other with

only gradual changes as their atomic numbers increase.

(a) The fixed oxidation number of Group II elements in their compounds.

Interpretation in terms of the electronic structure of the elements.

(b) Thermal decomposition of nitrates, carbonates and hydroxides.

The alkaline earth metals are a series of elements comprising Group 2

(IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg),

calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The alkaline

earth metals provide a good example of group trends in properties in the

periodic table, with well characterised homologous behaviour down the

group.
http://en.wikipedia.org/wiki/Chemical_serieshttp://en.wikipedia.org/wiki/Chemical_elementhttp://en.wikipedia.org/wiki/Periodic_table_grouphttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Periodic_tablehttp://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Strontiumhttp://en.wikipedia.org/wiki/Bariumhttp://en.wikipedia.org/wiki/Radiumhttp://en.wikipedia.org/wiki/Chemical_elementhttp://en.wikipedia.org/wiki/Periodic_table_grouphttp://en.wikipedia.org/wiki/IUPAChttp://en.wikipedia.org/wiki/Periodic_tablehttp://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Strontiumhttp://en.wikipedia.org/wiki/Bariumhttp://en.wikipedia.org/wiki/Radiumhttp://en.wikipedia.org/wiki/Chemical_series


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beryllium is an exception: It does not react with water or steam, and its

halides are covalent.

All the alkaline earth metals have two electrons in their outermost shell, so

the energetically preferred state of achieving a filled electron shell is to lose

two electrons to form doubly chargedpositiveions.

The alkaline earth metals are silvery colored, soft, low-density metals, which

react readily with halogens to form ionic salts, and with water, though not as

rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. Forexample, where sodium andpotassium react with water at room temperature,

magnesium reacts only with steam and calcium with hot water:

Mg + 2 H2O Mg(OH)2 + H2

5.2 Nitrogen

(a) The element: reasons for its lack of reactivity.

(b) Ammonia

(i) Manufacture by the Haber process.

Reference should be made to application of the principles of kinetics

and equilibria to this process.

(ii) Formation from ammonium salts.

(iii) Properties as a base.

(iv) Uses, particularly in the manufacture of nitric acid and fertilisers.
http://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_shellhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Positivehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Halogenhttp://en.wikipedia.org/wiki/Ionic_salthttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Alkali_metalhttp://en.wikipedia.org/wiki/Alkalihttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Berylliumhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_shellhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Positivehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Halogenhttp://en.wikipedia.org/wiki/Ionic_salthttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Alkali_metalhttp://en.wikipedia.org/wiki/Alkalihttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Calcium


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5.3 Group VII

Halogens are highly reactive, and as such can be harmful or lethal to

biological organisms in sufficient quantities. This high reactivity is due to

their atoms being one electron short of a full outer shell of eight electrons.

They can gain this electron by reacting with atoms of other elements.

Fluorine is the most reactive element in existence, attacking such inert

materials as glass, and forming compounds with the heaviernoble gases. It

is a corrosive and highly toxic gas. The reactivity of fluorine is such that, ifused or stored in laboratory glassware, it can react with glass in the presence

of small amounts of water to form SiF4. Thus fluorine must be handled with

substances such as Teflon, extremely dry glass, or metals such as copper or

steel which form a protective layer of fluoride on their surface.

.

5.4 An Introduction to the Chemistry of some d-block Elements

The first row d-block (transition) elements chromium, manganese, iron,

nickel and copper.

Emphasis should be place on the similarity of the elements to each other and

the interpretation of their properties, where appropriate, in terms of

incomplete d subshells.

(a) The physical properties of transition metals: melting points, density,

successive

ionisation energies (up to the fourth, where appropriate).

(b) Characteristic chemical properties of these elements.
http://en.wikipedia.org/wiki/Reactivityhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Fluorinehttp://en.wikipedia.org/wiki/Noble_gaseshttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Reactivityhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Fluorinehttp://en.wikipedia.org/wiki/Noble_gaseshttp://en.wikipedia.org/wiki/Polytetrafluoroethylene


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(i) Variable oxidation state and colour: the principal oxidation

states/numbers of these elements in their common cations, oxides and oxo-

anions, the relative stabilities of these oxidation states.

(ii) Formation of complex ions; exchange of ligands.

No treatment of stability constants is expected.

It is expected that candidates will be familiar with the hexa-aquo ions of

the above elements, the corresponding ammine complexes, where

appropriate, and the [CuCl4]2 ion.

No treatment of the geometry of complexes is required.No treatment of bonding in complexes is required.

(iii) Catalytic properties, transition metals and their compounds as

important industrial catalysts, e.g. Fe/Fe2O3 in the Haber process, Ni in the

hydrogenation of alkenes.


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6 THE STRUCTURES OF ORGANIC MOLECULES


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7 ELECTRONIC EFFECTS AND REACTION TYPES

The nature of the C-H, C-Br and > C = C < and > C = O bonds in terms of

electron density distribution.


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Heterolytic and homolytic bond fission; nucleophiles and electrophiles.

Reaction types; addition, substitution and elimination. Addition and

substitution classified as electrophilic, nucleophilic (reference to SN1 and

SN2 mechanisms is not required) or free radical.

8 GENERAL ORGANIC CHEMISTRY

Wherever possible the above classification of reaction types should beindicated.

8.1 Hydrocarbons

Alkanes Cracking reactions as a means of obtaining alkenes from crude oil

fractions.

Alkanes as being generally characterised by free radical reactions, e.g.

reaction with bromine.

Alkenes Characterised by electrophilic addition, e.g. HBr, Br2. Simple

tests for alkenes by decolourisation of manganate (VII) ions and of bromine

in an inert solvent.

Catalytic hydrogenation to alkanes.

Arenes Characterised by electrophilic substitution, e.g. AlBr3/Br2, conc.

HNO3/H2SO4. (Monosubstitution only).

8.2 Halogen derivatives

Halogenoalkanes characterised by nucleophilic substitution, e.g. OH , CN.

Difficulties of nucleophilic substitution in halogenoarenes.


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Haloalkanes are reactive towards nucleophiles. They are polar molecules:

the carbon to which the halogen is attached is slightly electropositive where

the halogen is slightly electronegative. This results in an electron deficient

(electrophilic) carbon which, inevitably, attracts nucleophiles.

Substitution reactions

Substitution reactions involve the replacement of the halogen with another

molecule - thus leaving saturated hydrocarbons, as well as the halogen

product.

Hydrolysis - a reaction in which waterbreaks a bond--is a good example ofthe nucleophilic nature of halogenoalkanes. The polar bond attracts a

hydroxide ion, OH-. (NaOH(aq) being a common source of this ion). This

OH- is a nucleophile with a clearly negative charge, as it has excess

electrons it donates them to the carbon, which results in a covalent bond

between the two. Thus C-X is broken by heterolytic fission resulting in a

halide ion, X-. As can be seen, the OH is now attached to the alkyl group,

creating an alcohol. (Hydrolysis of bromoethane, for example, yields

ethanol).

One should note that within the halogen series, the C-X bond weakens as

one goes to heavier halogens, and this affects the rate of reaction. Thus, the

C-I of an iodoalkane generally reacts faster than the C-F of a fluoroalkane.

Apart from hydrolysis, there are a few other isolated examples of

nucleophilic substitution:

Ammonia (NH3) and bromoethane yields a mixture of ethylamine,

diethylamine, and triethylamine (as their bromide salts), and

tetraethylammonium bromide.

Cyanide (CN-) added to bromoethane will formpropionitrile (CH3CH2CN), a

nitrile, and Br-. Nitriles can be further hydrolyzed into carboxylic acids.
http://en.wikipedia.org/wiki/Nucleophilehttp://en.wikipedia.org/wiki/Polarityhttp://en.wikipedia.org/wiki/Electropositivehttp://en.wikipedia.org/wiki/Electronegativehttp://en.wikipedia.org/wiki/Electron_deficiencyhttp://en.wikipedia.org/wiki/Nucleophileshttp://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Saturated_hydrocarbonhttp://en.wikipedia.org/wiki/Hydrolysishttp://en.wikipedia.org/wiki/Water_(molecule)http://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Ethylaminehttp://en.wikipedia.org/wiki/Diethylaminehttp://en.wikipedia.org/wiki/Triethylaminehttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/w/index.php?title=Tetraethylammonium_bromide&action=edithttp://en.wikipedia.org/wiki/Cyanidehttp://en.wikipedia.org/wiki/Propionitrilehttp://en.wikipedia.org/wiki/Nitrilehttp://en.wikipedia.org/wiki/Carboxylic_acidhttp://en.wikipedia.org/wiki/Nucleophilehttp://en.wikipedia.org/wiki/Polarityhttp://en.wikipedia.org/wiki/Electropositivehttp://en.wikipedia.org/wiki/Electronegativehttp://en.wikipedia.org/wiki/Electron_deficiencyhttp://en.wikipedia.org/wiki/Nucleophileshttp://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Saturated_hydrocarbonhttp://en.wikipedia.org/wiki/Hydrolysishttp://en.wikipedia.org/wiki/Water_(molecule)http://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Ethylaminehttp://en.wikipedia.org/wiki/Diethylaminehttp://en.wikipedia.org/wiki/Triethylaminehttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/w/index.php?title=Tetraethylammonium_bromide&action=edithttp://en.wikipedia.org/wiki/Cyanidehttp://en.wikipedia.org/wiki/Propionitrilehttp://en.wikipedia.org/wiki/Nitrilehttp://en.wikipedia.org/wiki/Carboxylic_acid


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8.3 Hydroxy compounds

Primary, secondary and tertiary alcohols; reactions with acids, e.g. HBr,

H2SO4 leading to substitution and elimination. Oxidisation of primary and

secondary alcohols resistance to mild oxidation by tertiary alcohols. Ester

formation with organic acids and acyl chlorides. Tests for presence of

hydroxyl group using sodium or phosphorus pentachloride.

Phenols acidity compared to alcohols and carboxylic acids; ease of

electrophilic substitution compared with benzene.

8.4 Carbonyl compounds

(a) Aldehydes; ease of oxidation; reduction to primary alcohol; condensation

with hydroxylamine.

(b) Ketones; more resistant to oxidation, reduction to secondary alcohol;

condensation with hydroxylamine.

Tests based on alkaline Cu2+ complex to distinguish between aldehydes and

ketones.

8.5 Carboxylic acids and derivatives

Carboxylic acids; acidity compared to alcohols and phenols. Formation from

alcohols.

Reduction to alcohols. Conversion to esters, acyl chlorides.

Acyl chlorides; treated as reactive derivatives carboxylic acids widely used

in the synthesis of amides and esters.

8.6 Amines


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Aliphatic primary amines; basic properties. Reaction with nitrous acid.

Formation from nitriles. Aromatic primary amines; their formation from

aromatic nitro compounds; basic properties. Reaction with nitrous acid and

production azo dyes.

As displayed in the image, primary aliphatic amines arise when

one of three hydrogen atoms in ammonia is replaced by an organic

substituent.


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