carbon anode/+ (1) electrolyte Al 2 O 3 with or dissolved in or solution in cathode/ (1) (steel outer)

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1 1. Aluminium occurs as bauxite, which contains aluminium oxide with impurities mainly of iron (III) oxide and silica. (a) (b) (c) Outline how bauxite is processed to give pure aluminium oxide, showing clearly the chemical basis for the method. AI 2 O 3 is amphoteric Impurities are not Heat with aq NaOH Filter out Si and Fe compounds Balanced equation for reaction AI 2 O 3 + OH Re pptn by seeding or CO 2 AI(OH) 3 / AI 2 O 3 Aluminium is produced by electrolysis of purified aluminium oxide. State briefly the necessary conditions, sketch and label the cell used. Give the reaction of each electrode. electrolyte Al 2 O 3 with molten Na 3 AlF 6 /cryolite or dissolved in or solution in carbon anode/+ cathode/ (steel outer) anode: O2 ½O 2 + 2e cathode: AI3+ + 3e AI Two correct equations but anode and cathode wrong way or left out max (Allow balanced equation for reaction of an aluminate ion) Electrolysis is very expensive. Whit is it used for aluminium production but not for iron? AI 2 O 3 not reducible by C/CO at low temperature too high in reactivity / electrochemical series not AI 2 O 3 stable (d) (i) Sketch the structure of aluminium chloride, which has a molar mass of 267 g mol 1 in the vapour state, to show the bonding present. [You are not required to show the shape of this molecule.] Cl Cl Cl Al Al or dot and cross Cl Cl Cl either arrow or line (no need to show bond angles) (5) (5) (2) Why does aluminium chloride adopt this structure? AI electron deficient / empty orbital / acts as Lewis acid and dimerisation 'overcomes' this or attains noble gas electron structure (Total 15 marks) NT Exampro 1

2 2. Aluminium occurs as bauxite, which contains aluminium oxide with impurities mainly of iron (III) oxide and silica. Outline how bauxite is processed to give pure aluminium oxide, showing clearly the chemical basis for the method. AI 2 O 3 is amphoteric Impurities are not Heat with aq NaOH Filter out Si and Fe compounds Balanced equation for reaction AI 2 O 3 + OH Re-pptn by seeding or CO 2 AI(OH) 3 / AI 2 O 3 (Total 5 marks) 3. Aluminium is produced by electrolysis of purified aluminium oxide. State briefly the necessary conditions, sketch and label the cell used. Give the reaction of each electrode. electrolyte Al 2 O 3 with molten Na 3 AlF 6 /cryolite or dissolved in or solution in carbon anode/+ cathode/ (steel outer) anode: O2 ½O 2 + 2e cathode: AI3+ + 3e AI Two correct equations but anode and cathode wrong way or left out max (Allow balanced equation for reaction of an aluminate ion) 4. Sodium and sodium hydroxide are both manufactured by electrolytic processes. (a) Name the electrolyte used in the manufacture of: sodium hydroxide: aqueous (½) sodium chloride / NaCI (½) sodium chloride solution brine (½) (Total 5 marks) NT Exampro 2

3 (b) (i) What is produced at the anode during the manufacture of sodium hydroxide? Write an equation for its formation. Product chlorine Equation CI ½CI 2 + e( ) (c) Product oxygen Equation 2OH ½O 2 + H 2 O + 2e( ) (2) species balance not O2- If CI 2 /O 2 in wrong places, can get equation marks Suggest a reason why the product in (b)(i) is formed in the industrial process rather than that in (b). OH more easily oxidised E value less positive / under standard conditions but CI present in greater concentration / OH much lower concentration OR argument based on use of chlorine eg reaction of chlorine with OH ions to form CIO or CIO 3 an equation some correct reference to temperature 5. (a) Electrolysis of brine under different conditions gives sodium chlorate(i); in this case the sodium hydroxide and chlorine are allowed to mix t room temperature. (b) (i) (5) (Total 9 marks) Give the ionic equation for the reaction of chlorine with cold dilute aqueous sodium hydroxide. Cl 2 + 2OH OCl + Cl + H 2 0 ignore Na+ on either side if ionic equation not given (0) If the solution of sodium chlorate(i) is heated, the chlorate(i) ion disproprortionates. Write the ionic equation for the reaction, and use it to explain the meaning of disproportionation. 3OCl 2 Cl + Cl0 3 include oxidation states of products same species both oxidised and reduced Give one use for any suitable specific uses water sterilisation / manufacture of polymers / PVC / bleach NT Exampro 3

4 (c) Suggest how using a solution of sodium chlorate(i), or otherwise, you could distinguish between separate aqueous solutions of potassium bromide and potassium iodide. acidify or use of chlorine shake with immiscible organic solvent/hexane/ccl 4 brown colour shows Br purple colour shows I OR equivalent using AgNO 3 (½) to solution of each or AgNO 3 drop by drop cream ppt from Br (½) yellow ppt from I (½) add (conc) NH 3 AgBr dissolves (½) AgI insoluble (½) (4) (Total 9 marks) 6. Electrolysis of brine under different conditions gives sodium chlorate(i); in this case the sodium hydroxide and chlorine are allowed to mix t room temperature. (a) (b) Give the ionic equation for the reaction of chlorine with cold dilute aqueous sodium hydroxide. Cl 2 + 2OH OCl + Cl + H 2 O ignore Na+ on either side if ionic equation not given (0) If the solution of sodium chlorate(i) is heated, the chlorate(i) ion disproprortionates. Write the ionic equation for the reaction, and use it to explain the meaning of disproportionation. 3OCl 2 Cl + ClO 3 include oxidation states of products same species both oxidised and reduced (Total 4 marks) 7. (a) (i) 2 3 (iii) 2 (iv) 2 or 4 or 6 (v) 2 or 6 (vi) 5 (vii) 2 or 4 (viii) 1 or 6 8 (b) (i) 2Na(s) + 2H 2 O(l) 2NaOH(aq) + H 2 (g) CaO(s) + H 2 O(l) Ca(OH) 2 (aq) (iii) MgCO 3 (s) MgO(s) + CO 2 (g) (iv) Cl 2 (g) + 2KBr(aq) 2KCl(aq) + Br 2 (aq) (v) 2NaCl(aq)+2H 2 O(l) 2NaOH(aq) + Cl 2 (g) + H 2 (g) 5 [13] 8. (a) (i) 2SO 2 + O 2 2SO 3 1 vanadium(v) oxide / vanadium V oxide / V 2 O 5 / vanadium NT Exampro 4

5 (iii) pentoxide C / K 2-5 atm n.b. any stated number or range within the above ranges 3 Any one use production of fertilizers, detergents, dyes, paints, pharmaceuticals, rayon (in) car batteries, pickling metal 1 (b) (i) bauxite 1 Al3+ + 3e Al 2O2 O 2 + 4e 2 (iii) Graphite /carbon 1 (iv) electricity / power / energy / fuel 1 (v) conserves resources of ores or bauxite uses less energy/power/electricity/fuel (than extraction) / conserves energy resources 2 (vi) e.g. aeroplanes, cans, power cables, window frames, car bodies, car engine blocks, foil, bicycle frames, kitchen utensils 1 9. (a) (i) Aqueous sodium chloride or sodium chloride solution or brine or concentrated sodium chloride formula or words chlorine/ Cl 2 but not Cl hydrogen / H 2 but not H 2 (iii) 2NaCl + 2H 2 O 2NaOH + H 2 + Cl 2 Formulae, balance. 2 (iv) Salt water does not evolve Cl 2 or other sensible suggestion showing understanding that chlorine, hydrogen or sodium hydroxide is not 1 produced when salt is added to water. (v) Prevents reaction of chlorine and sodium hydroxide (specifically) or allow cations / only Na+ ions to pass through or prevents reaction of / mixing of chlorine and alkali 1 (b) (i) Cl 2 (aq / g) + 2OH (aq) OCl (aq) + Cl (aq) + H 2 O species balance states. 3 Need correct species to score balance and / or state marks Any from: Chlorine changes oxidation states. Chlorine disproportionates / chlorine gains and loses electron Chlorine goes from to 0 to 1 or 0 to +1 Chlorine is both oxidised and reduced 1 [13] NT Exampro 5

6 (iii) Bleach or disinfectant. 1 [12] 10. (a) (i) Al 2 O 3 / Al 2 O 3.xH 2 O 1 lron(iii) oxide / Fe 2 O 3 NOT iron(ii) oxide silica / silicon (di)oxide / SiO 2 NOT sand 2 (iii) Al 2 O 3 reacts because it is amphoteric Dissolves / forms a solution IF silica dissolves then 2nd mark is lost. Impurities don t react / dissolve because Fe 2 O 3 basic / silica too unreactive 3 (b) (i) Graphite / carbon NOT C 1 Al3+ + 3e(-) Al IGNORE state symbols UNLESS (aq) given, in which case 0. 1 (iii) Carbon anode reacts with oxygen Gas / CO 2 given off / CO 2 (g) NOT CO 2 formed 2 [10] NT Exampro 6