i) What is the name of the process used for the industrial preparation of tetraoxosulphate (VI) acid?
(ii) State the catalyst used in (a)(i)
(iii) Show by means of bdanced chemical equations only, the industrial preparation of tetraoxosulphate (VI) acid from sulphur (IV) oxide.
(b)(i) Distinguish between dehydration and drying
(ii) Explain why concentrated tetraoxosulphate (VI) acid cannot be used to dry ammonia
(iii) What is the drying agent for ammonia?
(c)(i) Give one example of I. a chloride which is soluble in hot water, II. a trioxocarbonate (IV) which does not decompose on heating, Ill. an amphoteric oxide
(ii) List three methods for the preparation of salts
(iii) State one method for the recovery of salt from its solution.
(d)(i) State Gay Lussac's law of combining volumes
(ii) Consider the reaction represented by the following equation: C\(_2\)H\(_{4(g)}\) + 3O\(_{2(g)}\) \(\to\) 2H\(_2\)O\(_{(g)}\) + 2CO\(_{2(g)}\). What is the volume of oxygen required for the complete combustion of 12.5 cm\(^{3}\) of ethene?
(a) Industrial preparation of tetraoxosulphate(VI) acid
- (i) Process: the Contact process.
- (ii) Catalyst: vanadium(V) oxide, V2O5 (platinised asbestos may also be used).
- (iii) From sulphur(IV) oxide: \[2SO_2 + O_2 \rightleftharpoons 2SO_3\] \[SO_3 + H_2SO_4 \rightarrow H_2S_2O_7\] \[H_2S_2O_7 + H_2O \rightarrow 2H_2SO_4\]
(b) Dehydration and drying
- (i) Dehydration is the removal of the chemically combined elements of water (hydrogen and oxygen in the ratio 2:1) from a compound, a chemical change; drying is the removal of free (physically held) moisture from a substance without changing its chemical composition, a physical change.
- (ii) Concentrated H2SO4 cannot dry ammonia because the acid reacts with ammonia (a base): \[2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4\] so it absorbs the gas instead of merely drying it.
- (iii) Drying agent for ammonia: calcium oxide (quicklime, CaO).
(c) Salts
- (i) I. Chloride soluble in hot water (but not cold): lead(II) chloride, PbCl2. II. Trioxocarbonate(IV) that does not decompose on heating: sodium trioxocarbonate(IV), Na2CO3. III. Amphoteric oxide: aluminium oxide, Al2O3 (or ZnO).
- (ii) Three methods of preparing salts: neutralisation of an acid with a base or alkali; action of an acid on a metal; action of an acid on a trioxocarbonate(IV) (also precipitation/double decomposition).
- (iii) Recovery of a soluble salt from solution: evaporation of the solution to the point of crystallisation, then cooling to crystallise.
(d) Gay-Lussac's law and combustion of ethene
- (i) Gay-Lussac's law of combining volumes: when gases react, they do so in volumes that bear a simple whole-number ratio to one another and to the volumes of any gaseous products, provided temperature and pressure are constant.
- (ii) From \(C_2H_4 + 3O_2 \rightarrow 2H_2O + 2CO_2\), the volume ratio of ethene to oxygen is 1:3, so \[V(O_2) = 3 \times 12.5 = 37.5\text{ cm}^3\]
(a) Industrial preparation of tetraoxosulphate(VI) acid
- (i) Process: the Contact process.
- (ii) Catalyst: vanadium(V) oxide, V2O5 (platinised asbestos may also be used).
- (iii) From sulphur(IV) oxide: \[2SO_2 + O_2 \rightleftharpoons 2SO_3\] \[SO_3 + H_2SO_4 \rightarrow H_2S_2O_7\] \[H_2S_2O_7 + H_2O \rightarrow 2H_2SO_4\]
(b) Dehydration and drying
- (i) Dehydration is the removal of the chemically combined elements of water (hydrogen and oxygen in the ratio 2:1) from a compound, a chemical change; drying is the removal of free (physically held) moisture from a substance without changing its chemical composition, a physical change.
- (ii) Concentrated H2SO4 cannot dry ammonia because the acid reacts with ammonia (a base): \[2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4\] so it absorbs the gas instead of merely drying it.
- (iii) Drying agent for ammonia: calcium oxide (quicklime, CaO).
(c) Salts
- (i) I. Chloride soluble in hot water (but not cold): lead(II) chloride, PbCl2. II. Trioxocarbonate(IV) that does not decompose on heating: sodium trioxocarbonate(IV), Na2CO3. III. Amphoteric oxide: aluminium oxide, Al2O3 (or ZnO).
- (ii) Three methods of preparing salts: neutralisation of an acid with a base or alkali; action of an acid on a metal; action of an acid on a trioxocarbonate(IV) (also precipitation/double decomposition).
- (iii) Recovery of a soluble salt from solution: evaporation of the solution to the point of crystallisation, then cooling to crystallise.
(d) Gay-Lussac's law and combustion of ethene
- (i) Gay-Lussac's law of combining volumes: when gases react, they do so in volumes that bear a simple whole-number ratio to one another and to the volumes of any gaseous products, provided temperature and pressure are constant.
- (ii) From \(C_2H_4 + 3O_2 \rightarrow 2H_2O + 2CO_2\), the volume ratio of ethene to oxygen is 1:3, so \[V(O_2) = 3 \times 12.5 = 37.5\text{ cm}^3\]
