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UNIT 1 REVISION CHECKLIST Topic 1.1 Can you a) define atomic number, mass number, isotopes, relative atomic mass, relative molecular mass b) remember the four stages in mass spectrometry and explain how each one w orks c) calculate relative atomic mass from isotopic composition data, or from a mass spectrum of an atom d) deduce relative molecular mass from the mass spectrum of a molecule e) Give the electronic configuration of atoms with atomic number 1-36 and of the common ions of elements 1 - 18 f) Define 1 st ,2 nd ionisation energy g) Explain trends in 1 st IE across period (general increase, decrease from Be to B, decrease from N to O) and down group h) Explain trends in successive ionisation energies i) Explain why isotopes have similar chemical properties Topic 1.2 Can you: a) recall the formulae of simple cations and anions from the name b) write balanced chemical equations given all the reactants and products in words c) interconvert the units of mass (mg, g, kg, tonnes) and volume (cm 3 , dm 3 , m 3 ) d) recall and apply the relationship between mass, molar mass and number of moles e) deduce reacting masses and how much of one substance can be obtained from a given mass of another f) state the ideal gas equation and use it to relate gaseous volume to number of moles

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UNIT 1 REVISION CHECKLIST

Topic 1.1 Can you a) define atomic number, mass number, isotopes, relative atomic mass, relative molecular mass

b) remember the four stages in mass spectrometry and explain how each one w orks

c) calculate relative atomic mass from isotopic composition data, or from a mass spectrum of an atom

d) deduce relative molecular mass from the mass spectrum of a molecule

e) Give the electronic configuration of atoms with atomic number 1-36 and of the common ions of elements 1 - 18

f) Define 1st,2nd ionisation energy g) Explain trends in 1st IE across period (general increase, decrease from Be to B, decrease from N to O) and down group

h) Explain trends in successive ionisation energies i) Explain why isotopes have similar chemical properties Topic 1.2 Can you: a) recall the formulae of simple cations and anions from the name

b) write balanced chemical equations given all the reactants and products in words

c) interconvert the units of mass (mg, g, kg, tonnes) and volume (cm3, dm3, m3)

d) recall and apply the relationship between mass, molar mass and number of moles

e) deduce reacting masses and how much of one substance can be obtained from a given mass of another

f) state the ideal gas equation and use it to relate gaseous volume to number of moles

g) deduce the number of particles from the number of moles and vice versa from Avogadro's number

h) recall and apply the relationship between number of moles, volume, concentration (moldm-3 and gdm-3) of solutions

i) deduce empirical and molecular formula from suitable data Topic 1.3 Can you: a) define an ionic bond, covalent bond, metallic bond, and predict the type of bonding present in simple substances

b) explain the difference between normal and dative covalent bonds

c) define electronegativity and use it to explain why some bonds are covalent, others polar covalent and others ionic

d) draw dot-cross diagrams to show ionic and covalent bonding e) explain the processes taking place when a solid is heated until it melts and then boils

f) explain the existence of four different types of substance - ionic, metallic, molecular and macromolecular - and the different properties of these structures (mpt, bpt, electrical conductivity) – using diamond, graphite, iodine, sodium chloride, magnesium and ice as specific examples

g) predict and explain the shapes of simple molecules, giant covalent structures and ions using the electron pair repulsion theory, limited to 2, 3, 4, 5 and 6 electron pairs

h) predict whether or not a molecule will be polar, and hence deduce the type of intermolecular force acting between the molecules

i) use intermolecular forces to explain trend in boiling point of simple molecular substances

Topic 1.4 Can you: a) Define s-block, p-block, d-block elements b) Explain trends in size, ionisation energy and electronegativity in period 3 and group II

c) Predict trends in melting and boiling point of elements in

period 3 and group II and explain using the structure and bonding in the elements d) Predict and explain trends in electrical conductivity in period 3

Topic 1.5 Can you:

• Draw displayed formulae and write clear structural formulae for alkanes, alkenes and haloalkanes, containing up to six carbon atoms

• Name simple alkanes, alkenes and haloalkanes,

containing up to six carbon atoms

• Explain the terms empirical formula, molecular formula,

homologous series and functional group, and be able to identify the functional group from the molecular formula.

• Explain the term isomerism, distinguish between

positional, chain and functional isomerism, draw all possible isomers of alkanes, alkenes and haloalkanes for molecules with up to four carbon atoms, and recognise isomerism in larger molecules.

Topic 1.6 Can you:

• Explain what crude oil is, how fractional distillation works and why it is necessary.

• Know the names of the major fractions, and their main

uses.

• Explain how cracking works and w hy it is necessary,

distinguish between thermal and catalytic cracking and know the conditions, products and uses for both types of cracking.

• Be able to write equations for the complete and

incomplete combustion of hydrocarbons, account for the formation of the oxides of nitrogen and sulphur, identify the main pollutants and know the specific problem associated with each.

• Explain the role of catalytic converters in reducing

pollution.

UNIT 2 REVISION CHECKLIST

Topic 2.1 Energetics Can you: a) understand that reactions are either exothermic or endothermic and apply the sign convention

b) define the term “enthalpy change”, recall what standard conditions are and understand that conditions affect enthalpy changes

c) define activation energy and relate it to bond breaking d) recall and use q = mc∆T and ∆H = q/n and explain how simple enthalpy changes are measured

e) use bond dissociation enthalpy data to calculate approximate enthalpy changes and vice versa

f) Define Hess' Law , standard enthalpy of formation and standard enthalpy of combustion

g) Calculate enthalpy changes from enthalpy of formation data using Hess' Law and vice versa

h) Calculate enthalpy changes from enthalpy of combustion data using Hess' Law and vice versa

Topic 2.2 Kinetics Can you: a) Explain collision theory in terms of collision frequency, collision energy, activation energy and the fraction of successful collisions

b) Outline an experimental procedure for measuring the rate of a reaction which involves a gas being evolved

c) Sketch graphs to show how the concentration of a reactant varies with time in a chemical reaction and know that the gradient of the graph is the rate of the reaction

d) Sketch the Maxwell-Boltzmann distribution of molecular energies at two temperatures

e) Explain the large effect on rate of reaction of a small increase in temperature by reference to Maxwell-Boltzman,

collision energy, fraction of successful collisions and collision frequency f) Define the term "catalyst" and explain that the catalyst lowers the activation energy by providing an alternative reaction pathway

g) Explain by reference to Maxwell-Boltzmann how a catalyst increases the rate of a reaction

h) Explain how concentration, pressure and particle size affect the rate of a reaction

Topic 2.3 Equilibria Can you: a) Explain the term "dynamic equilibrium" and recall that all equilibria are dynamic

b) Use Le Chatelier's Principle to explain the effect of changes in temperature, pressure, concentration and catalysts on the position of equilibrium, and select suitable conditions to maximise the yield of a certain product

c) Explain that reaction conditions used in industry sometimes differ from those which would maximise the yield due to the importance of rate of reaction and cost of energy, equipment and maintenance

Topic 2.4 Redox Reactions Can you: a) Define oxidation and reduction in terms of electron transfer b) deduce half-equations for oxidation and reduction processes and hence derive ionic equations for redox reactions

c) define the terms oxidising and reducing agent and recognise them in chemical reactions

Topic 2.5 Group VII, The Halogens Can you: a) describe the trends in physical appearance, boiling point, electronegativity and oxidising power of the halogens, and known the different colours of iodine in vapour, solid and aqueous form

b) write equations and observations for the displacement reactions of halogens with halide ions

c) describe and explain the trend in reducing power of the halides, and write equations and give observations for the reactions of solid halides with concentrated sulphuric acid

d) describe how nitric acid and silver nitrate can be used to distinguish between aqueous halide ions, and know the solubility of the silver halides in ammonia

e) write equations for the reactions of chlorine with water and dilute NaOH and know the uses of the solutions formed

Topic 2.6 Group 2, the Alkaline Earth Metals Can you:

a) describe and explain the trends in electronegativity and melting point of the elements in group 2

b) describe the reactions of Mg with steam and of Ca, Sr

and Ba with water and write appropriate equations

c) describe the trends in the solubility of hydroxides and

sulphates write ionic precipitation equations where appropriate

d) know that acidified barium chloride can be used as a

test for sulphate ions

e) know the uses of magnesium hydroxide, calcium

hydroxide and barium sulphate

Topic 2.7 Extraction of Metals Can you: a) know that the most important methods of extracting metals from ores are reaction of the oxide with carbon (eg iron), reaction of the halide with a metal (eg titanium), electrolysis (eg aluminium) and reaction of the oxide with hydrogen (eg tungsten)

b) explain why different methods are appropriate for different metals

c) describe the reactions taking place in the blast furnace and explain how the furnace is heated, how the CO is produced, how the iron ore is reduced and how the silicon dioxide is removed

d) know how slag is removed from the furnace and know its uses

e) know that this process is also used to extract other metals which exist as sulphides, know that the sulphides have to be converted into the oxides by roasting in air and know why this causes pollution

f) know that aluminium is extracted by electrolysis of its purified oxide, know the electrode reactions, know what the electrodes are made of, understand the role of the molten cryolite and explain why the anodes need to be regularly replaced

g) know that titanium dioxide is converted into its chloride by reaction with carbon and chlorine, and that the chloride is reduced by sodium or magnesium, and know the equations and conditions for both reactions

h) explain why the aluminium and titanium extractions are expensive and why titanium cannot be extracted by any other method

i) explain how tungsten is extracted from its oxide by hydrogen

j) explain the main barriers to recycling, explain why recycling is economically and environmentally desirable and explain how iron and aluminium are recycled

2.8 Haloalkanes Can you: a) give the mechanism for the reaction between methane and chlorine, give the name of each step and know how termination and further propagation steps can give a number of different products

b) know that chloroalkanes and chlorofluoroalkanes are used as solvents

c) explain with aid of equations how chlorine radicals can destroy the ozone layer

d) escribe the structure and bonding in haloalkanes, use it to explain why they react with nucleophiles and explain how CN-, OH- and NH3 can behave as nucleophiles

e) Give the mechanisms for the nucleophilic substitution reactions of NH3, CN- and OH- with haloalkanes (including the role of ammonia as both base and nuleophile) and know the conditions for the reactions

f) recall that haloalkanes can undergo elimination in the presence of hydroxide ions, know the conditions which favour

elimination over substitution, understand that the two reactions compete and know the different roles of the hydroxide ion in both reactions g) Predict and explain whether one or two alkenes will be obtained from the elimination reaction

h) Recall that the rate of reaction of haloalkanes depends on the C-X bond enthalpy

2.9 Alkenes Can you: a) Explain and recognise geometrical isomerism in alkenes and name geometrical isomers

b) Describe the structure and bonding in alkenes, use it to explain why they react with electrophiles and explain how HBr, Br2 and H2SO4 can behave as electrophiles

c) Give the mechanism for the reaction of HBr, Br2 and H2SO4 with alkenes

d) Classify carbocation intermediates as primary, secondary or tertiary, recall that HBr and H2SO4 give two products with unsymmetrical alkenes, predict which of these products will be the major one and explain this on the basis of the stability of the carbocation intermediate

e) recall that the reaction between bromine and alkenes is used as a test for alkenes

f) recall the reagents, conditions and type of reaction involved in the hydration of alkenes to form alcohols

g) recall that alkylhydrogensulphates can be hydrolysed to form alcohols.

h) recall that alkenes can undergo addition polymerisation, deduce the monomer from the structure of a polymer and vice versa and know some uses of common polymers

2.10 Alcohols Can you: a) Recall the conditions for the fermentation of glucose to produce ethanol and understand the advantages and disadvantages of this method compared to the hydration of ethane, including the classification of ethanol as a biofuel

b) Give the reagents and conditions for the dehydration of

alcohols to form alkenes and predict and explain when two different alkenes will be formed c) Give the reagents and conditions for the oxidation of primary alcohols to aldehydes and then to carboxylic acids, of secondary alcohols to ketones

d) Describe and explain the simple chemical basis for the tests to distinguish between aldehydes and ketones

2.11 Analytical Techniques Can you:

a) deduce the molecular formula of a molecule from the accurate mass of the molecular ion

b) explain how fingerprinting of infra-red spectra allows

molecules to be identified

c) use infra-red spectra to identify functional groups

and impurities

d) explain how infra-red spectroscopy works and

understand how it can be used to explain global warming

If you can do all these things, you’ll get an A!

UNIT 4 REVISION CHECKLIST

Topic 4.1 Kinetics Can you: a) Define the terms: rate of a reaction, rate constant, order of reaction and overall order of reaction

b) Deduce the orders of reaction with respect to the reactants from initial rate data, presented graphically or in tabular form

c) Calculate the value of a rate constant and its units from initial rate data

d) Predict the effect of a change in temperature and pressure on the value of the rate constant

Topic 4.2 Equilibria Can you: a) Derive an expression for the equilibrium constant Kc of a chemical reaction, and deduce its units

b) Calculate the equilibrium constant of a reaction from equilibrium concentration data and vice versa

c) Calculate the equilibrium constant of a reaction from initial concentration data and some information relating to the equilibrium composition

d) Recall and explain that only temperature affects the value of the equilibrium constant

Topic 4.3 Acids and Bases Can you: a) Define the terms acid and base in terms of Bronsted-Lowry theory

b) Understand that acid-base reactions involve proton transfer and use the principle of acid-base conjugate pairs to explain acid-base reactions

c) Explain the terms strong acid, weak acid, strong base and weak base

d) Recall the expression for Kw (ionic product of water) and relate it to the auto-ionisation of water

e) Deduce an expression for Ka of weak acids f) Define the terms pH and pKa g) Calculate the pH of water and solutions of strong acids, weak acids or strong bases given the concentration and Kw or Ka, and vice versa, and explain the approximations involved

h) Explain why pH is temperature dependent and explain the variation of dissociation with temperature on the basis of the enthalpy changes of dissociation

i) Define the term buffer solution and explain using equations how a given buffer solution works

j) Calculate the pH of a buffer solution consisting of a mixture of a weak acid and its conjugate base using Ka and the relative concentrations of acid and base, and vice versa

k) Deduce the volume at which the end-point will be reached given information about the concentrations and volumes of the reacting species

l) Sketch titration curves for strong and weak acids with strong and weak bases

m) Understand that partially neutralised weak acids form a buffer solution, show how pH = pKa at half-neutralisation, and calculate the pH during titrations involving alkalis added to acids, including after excess alkali has been added

n) Select a suitable indicator for a given titration given pKin values, and explain the choice of indicator

o) Recall that polybasic acids form more than one salt on neutralization and write equations to show the formation of each salt

Topic 4.4 Nomenclature and Isomerism Can you: a) Name organic compounds involving all the functional groups introduced at AS level and also secondary and tertiary amines, quartenary ammonium salts, acid chlorides, acid anhydrides, amides, esters and N-substituted amides, and simple organic compounds involving two functional groups (such as amino acids)

b) Define the terms chiral, optical isomer (enantiomer) and

racemate, draw and recognise enantiomers and explain how they are distinguished, understand why some reactions produce racemates rather than single enantiomers, and explain why optical isomers of drugs may have very different effects Topic 4.5 Compounds Containing the Carbonyl Group a) Write equations for the oxidation and reduction of alcohols, carbonyls and carboxylic acids and recall suitable reagents and conditions for these redox reactions

b) Recall the reaction of carbonyls with HCN, and know the mechanism for nucleophilic addition limited to carbonyls with HCN and NaBH4.

c) Recall and write equations for the reaction of acid chlorides and acid anhydrides with water and ammonia

d) Recall and write equations for the reaction of carboxylic acid, acid chlorides and acid anhydrides with alcohols, and of acid chlorides and acid anhydrides with primary amines, and know why acid anhydrides are preferred to acid chlorides when preparing aspirin

e) Recall that esters can be hydrolysed under acidic and alkaline conditions and that this reaction is used in the manufacture of soap.

f) Describe how to make biodiesel from naturally occurring vegetable oil

e) Recall the mechanism of nucleophilic addition-elimination limited to acid chlorides with water, ammonia, primary amines and alcohols

Topic 4.6 Aromatic Chemistry Can you: a) Describe the structure and bonding in benzene and explain its stability

b) Write equations to show the nitration, acylation and alkylation of benzene, know the mechanism of electrophilic substitution limited to these reactions, know the necessary conditions and predict the major product formed when benzene is alkylated using alkenes and HCl

c) Write an equation for the reduction of nitrobenzene to phenylamine and give the reagents and conditions for the reaction

Topic 4.7 Amines Can you: a) Write equations for the formation of primary, secondary and tertiary amines and quartenary ammonium salts by reaction of a haloalkane with ammonia

b) Write equations for the formation of primary amines from nitriles and know the advantages of this method for preparing primary amines

c) Understand that amines are basic and write equations to show their basicity

d) Explain why aromatic amines are less basic than aliphatic amines

Topic 4.8 Amino Acids Can you: a) Name simple amino acids and draw their structures in high pH, low pH and as Zwitterions in the solid state

b) Recall that amino acids can undergo condensation reactions with each other and draw the structures of possible condensation products

c) Recall that amino acids can be separated by chromatography

Topic 4.9 Polymers Can you: a) Recall that alkenes can form addition polymers and draw structures for polymers given the monomer and vice versa

b) Recall that diacid chlorides or diacids can react with diols or diamines to form condensation polymers, draw the repeating units of polyesters and polyamides and know the structures of terylene and nylon 66

c) Understand how condensation polymers can be hydrolysed and understand the advantages and disadvantages of this

d) Understand that polyamides can form intermolecular and intramolecular hydrogen bonds and know the implications of this

e) Explain the problems of polymer disposal and recycling Topic 4.10 Organic Synthesis and Analysis Can you: a) Describe tests for aldehydes, alkenes and carboxylic acids and understand the chemistry underlying them

b) Describe how primary, secondary and tertiary alcohols could be distinguished

c) Describe how acid chlorides and acid anhydrides can be distinguished

d) Memorise a synthesis map showing the interconversion of all the different organic compounds and recall how one compound can be prepared from another using one or more steps

Topic 4.11 Structure Determination Can you: a) Write equations to show the fragmentation of molecular ions in a mass spectrum and predict the structures of the most likely fragmentation products

b) Use fragmentation patterns to deduce the structure of an organic compound given its molecular formula

c) Understand that molecules containing Cl or Br will have more than one molecular ion peak

d) Use data on infra-red absorption frequencies to deduce the functional groups present in an organic compound

e) Explain why TMS is a useful reference in proton nmr spectroscopy and why CCl4 and CDCl3 are useful solvents

f) Deduce the number of different proton environments and the number of protons in each environment from integrated proton nmr spectra

g) Deduce the number of different carbon environments from carbon-13 nmr spectra

g) Identify functional groups present in proton and carbon-13 nmr spectra from the chemical shift value

i) Predict and justify splitting patterns, and recall that

hydrogen atoms bonded to oxygen do not cause splitting j) Use integration factors, chemical shifts and splitting patterns to deduce structures of organic molecules

k) Describe what happens during gas-liquid chromatography

If you can do all these things, you will get an A!

UNIT 5 REVISION CHECKLIST

5.1 Thermodynamics You must be able to: a) Construct Born-Haber cycles using atomisation enthalpies, bond dissociation

enthalpies, enthalpies of vaporisation, 1st and 2nd ionisation enthalpies, 1st and 2nd electron affinities, and lattice enthalpies, define all these terms, and calculate the missing value if all other values and the enthalpy of formation is given

b) Use mean bond dissociation enthalpy data to calculate approximate enthalpy changes, and understand why these enthalpy changes are approximate

c) Construct a cycle to show the enthalpy changes which occur when ionic compounds dissolve in water, using lattice enthalpies, enthalpies of hydration and enthalpies of solution, define all these terms, and calculate the missing value if all others are given

d) Calculate entropy changes given the entropy of the reactants and products, and predict qualitatively whether the entropy change in a reaction will be positive or negative

e) Use enthalpy changes (ΔH) and entropy changes (ΔS) to calculate free energy changes (ΔG), understand that reactions are only spontaneous when ΔG is negative, and calculate the critical temperature above or below which a reaction will or will not be spontaneous

5.2 Periodicity You must be able to: a) Write equations for the reactions of Na and Mg with water, including the conditions necessary for the reactions to take place and any observations

b) Write equations for the reactions of Na, Mg, Al, Si, P and S with oxygen to form Na2O, MgO, Al2O3, SiO2, P4O10 and SO2, and relate the boiling points of these compounds to the structure and bonding present

c) Relate the acid-base character of these oxides, and also SO3, to the bonding present, write equations to show their reaction with water and give the pH of the resulting solutions, and write equations to show their reaction with simple acids

and bases 5.3 Redox Equilibria You must be able to: a) Deduce the oxidation number of an atom in an ion or compound, write half-equations to show oxidation or reduction processes, and write full ionic equations to show redox reactions in acidic and alkaline conditions

b) Draw simple chemical cells, represent them using conventional IUPAC notation, know the standard conditions, use standard electrode potential data to predict the direction of the reaction in a cell, calculate the cell emf and predict how a change in the conditions will affect the emf

c) Understand the use of the standard hydrogen electrode in measuring electrode potentials, and that secondary standard electrodes such as the calomel electrode are used in practice

d) Use standard electrode potentials to predict whether a redox reaction will be spontaneous or not

e) Know the reactions taking place in a hydrogen fuel cell and understand the advantages and limitations of fuel cells

5.4 Transition Metals You must be able to: a) Define a transition metal, and deduce the electronic configurations of the transition metals Ti – Cu and their ions

b) Define the terms ligand, complex ion and co-ordination number, explain why transition metal ions can bond with ligands, recall two examples of bidentate ligands and one example of a hexadentate ligand

c) Predict the likely co-ordination number and shape of a complex ion, and explain why larger ligands result in smaller co-ordination numbers

d) Explain why transition metal ions are coloured, describe the factors which can lead to a change in colour, and explain how colour can be used to determine concentration

e) Recall the structures and uses of haem and know why CO is toxic, and also recall the uses of cisplatin, [Ag(NH3)2]+,

[Ag(CN)2]- and [Ag(S2O3)2]3- f) Explain why transition metals can form a variety of oxidation states, and w rite half-equations for the reduction of Cr2O7

2- and VO2+ by zinc in acidic solution, the oxidation of

[Cr(OH)6]3- and Co(OH)2 by hydrogen peroxide in alkaline solution, and the oxidation of [Co(NH3)6]2+ by air in ammonia solution, and recall the colours of all the species produced

g) Write equations for the redox titrations involving manganate (VII) ions with Fe2+, H2O2 and C2O4

2- and involving Cr2O7

2- with Fe2+, describe how to carry out these titrations and perform calculations related to these calculations

h) Distinguish between homogeneous and heterogeneous catalysis, explain how a catalyst works, write equations to show the catalytic action of Fe2+ and Fe3+ in the reaction between S2O8

2- and I-, and explain how the reaction between MnO4-

and C2O42- is autocatalysed

i) Describe the stages of heterogeneous autocatalysis and explain catalytic activity in terms of a balance between adsorption and desorption, give examples of heterogeneous catalysis (Contact Process, Haber Process, hydrogenation of oils, catalytic converters), give equations to show how VO catalyses the Contact Process, explain the use of an inert ceramic support in catalytic converters and recall how Fe in the Haber process and Pt/Rh in catalytic converters can be poisoned

5.5 Reactions of Inorganic Compounds in Aqueous Solution

You must be able to: a) Define and recognise Lewis Acids and Bases b) Recall that most metal ions exist in aqueous solution as the hexaaqua complex, write equations to show why these complexes are acidic and explain why +3 complexes are more acidic than +2 complexes

c) Write equations to show the deprotonation of hexaaqua complexes of Fe2+, Cu2+ and Co2+ by hydroxide ions and ammonia, and of Fe3+, Cr3+, Al3+ by hydroxide ions, carbonate ions and ammonia to give hydroxide precipitates, know the colours of the precipitates formed and use equations to show how these deprotonation reactions can be reversed by the addition of acid

d) Write equations to show the deprotonation of

Cr(H2O)3(OH)3 and Al(H2O)3(OH)3 with excess hydroxide ions, recall the colours of the species formed and understand how this shows the amphoteric nature of these hydroxides e) Write equations to show the ligand exchange reactions of Cu(H2O)4(OH)2 and Co(H2O)4(OH)2 with excess ammonia, of Cu(H2O)6

2+ and Co(H2O)62+ with chloride ions, recall the

oxidation of Co(NH3)62+ on standing and recall the colours of

all the species formed

f) Write equations to show ligand exchange reactions of other aqueous ions with other ligands, including multidentate ligands, explain why substitution by chloride ions causes the co-ordination number to decrease and explain why substitution by multidentate ligands leads to the formation of more stable complexes (the chelate effect)

g) Write equations to show the precipitation reactions of the hexaaqua complexes of Fe2+, Cu2+ and Co2+ with carbonate ions to form carbonates, recall the colours of the precipitates formed and explain why they do not form hydroxides

h) Recall and w rite equations to show how Cr2O7

2- and CrO4

2- can be interconverted