10 5 This question concerns the combustion of fossil fuels in power stations. (a) One type of power station uses the combustion of methane gas to generate power. Write an equation for the incomplete combustion of methane gas to form carbon monoxide and water only. State symbols are not required. (2) (b) One of the problems associated with the combustion of some fossil fuels is the production of acidic gases, including the oxides of nitrogen and sulfur. (i) Explain how oxides of sulfur and nitrogen can be formed from the combustion of fossil fuels. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... Turn over 11 (ii) Some power stations use a process of flue gas desulfurisation (FGD) to remove sulfur oxides from the gaseous combustion products. One such process, known as wet scrubbing, uses a mixture of calcium carbonate and water to react with sulfur dioxide. Two relevant equations are SO2(g) + CaCO3(s) → CaSO3(s) + CO2(g) CaSO3(s) + 2H2O(l) + ½O2(g) → CaSO4·2H2O(s) Explain why this process is an incomplete solution to the problem of burning fossil fuels. Use the equations provided to illustrate your answer. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (c) Draw a dot‑and‑cross diagram for sulfur dioxide, showing outer electrons only. (1) (Total for Question 5 = 7 marks)