Hydrogen can be produced when steam and carbon monoxide are passed over a catalyst. H2O(g) + CO(g) ⇌ CO2(g) + H2(g) ΔH = −41 kJ/mol

1. (a)(i)The temperature of the equilibrium mixture is decreased. The pressure on the equilibrium mixture is kept constant. Describe how and explain why the position of equilibrium changes.[2]
2. (a)(ii)The pressure on the equilibrium mixture is increased. The temperature of the equilibrium mixture is kept constant. Explain why the change in pressure has no effect on this equilibrium.[1]
3. (b)Hydrogen is also produced when steam is passed over hot coke (carbon). This reaction is endothermic. H2O(g) + C(s) → CO(g) + H2(g)
4. (b)(i)On the axes below draw a labelled energy profile diagram for the reaction to show: • the reactants and products • the enthalpy change for the reaction • the activation energy of the reaction. [Figure: Blank energy profile diagram axes with 'energy' on y-axis and 'progress of reaction' on x-axis][3]
5. (b)(ii)The mixture of gases produced when steam is passed over hot coke also contains hydrogen sulfide, H2S, as an impurity. This can be removed by reacting the gas with moist iron(III) hydroxide. Complete the equation for this reaction. Fe(OH)3 + .... H2S → Fe2S3 + .... H2O [1][1]
6. (c)Fossil fuels contain small amounts of sulfur.
7. (c)(i)Describe how the combustion of fossil fuels leads to the formation of acid rain.[2]
8. (c)(ii)Describe one effect of acid rain on buildings.[1]

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