O-LevelChemistryRates of Reaction5070/22 · Oct/Nov 2019 · Q710 Marks

Sulfuric acid is made by the Contact process. 2SO2(g) + O2(g) ⇌ 2SO3(g) ∆H = –197kJ/mol

(a)Name the catalyst used in the Contact process.[1]
(b)(i)Describe how and explain why the position of equilibrium in the reaction is altered when: the temperature of the equilibrium mixture is increased at constant pressure[2]
(b)(ii)the pressure of the equilibrium mixture is increased at constant temperature.[2]
(c)The final step in the manufacture of sulfuric acid is an exothermic reaction. H2S2O7 + H2O = 2H2SO4 On the axes, draw a labelled energy profile diagram for this exothermic reaction. Show: • the reactants and product • the enthalpy change for the reaction • the activation energy of the reaction. [Diagram showing x-axis "progress of reaction" and y-axis "energy"][3]
(d)Air is a raw material used in the manufacture of sulfuric acid. Name one other raw material used in the manufacture of sulfuric acid.[1]
(e)State one major use of sulfuric acid.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[1] vanadium(V) oxide
[1] equilibrium moves to the left
[1] the (forward) reaction is exothermic / backward reaction endothermic / goes in the direction of the endothermic reaction
[1] equilibrium moves to the right
[1] fewer moles of gas on the right than on the left / more moles of gas on left than the right
[1] product to right of reactants and reactant level above product level
[1] enthalpy change shown as downward arrow and labelled
[1] activation energy drawn as energy hump above product level and labelled with upward arrow
[1] sulfur / water
[1] (making) detergents / fertilisers / battery acids

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