Sulfuric acid is made by the Contact process. One stage is the reaction between sulfur dioxide and oxygen to form sulfur trioxide.
2SO2(g)+O2(g)⇌2SO3(g)2\mathrm{SO_{2}(g)} + \mathrm{O_{2}(g)} \rightleftharpoons 2\mathrm{SO_{3}(g)}2SO2(g)+O2(g)⇌2SO3(g)
The forward reaction is exothermic. The industrial conditions are 450 °C, a pressure of 2 atm and a vanadium(V) oxide catalyst. Under these conditions about 99% of the sulfur dioxide is converted to sulfur trioxide.
Explain the effect of increasing the pressure on the equilibrium yield of sulfur trioxide.
Suggest why the plant uses a pressure of only 2 atm.
Explain the effect of increasing the temperature from 450 °C to 600 °C on the rate of attaining equilibrium and on the equilibrium yield of sulfur trioxide.
Calculate the volume of oxygen that reacts with 480 dm3\mathrm{dm^{3}}dm3 of sulfur dioxide. Both volumes are measured at the same temperature and pressure.
In a test run, 16 kg of sulfur dioxide is mixed with 3.2 kg of oxygen. Determine which reactant is the limiting reactant and calculate the maximum mass, in kg, of sulfur trioxide that can form. Relative formula masses: SO2=64,O2=32,SO3=80\mathrm{SO_{2}} = 64, \mathrm{O_{2}} = 32, \mathrm{SO_{3}} = 80SO2=64,O2=32,SO3=80
43 exam-style questions on Edexcel GCSE Chemistry 6.3 Dynamic equilibria, covering 6.3.1 The Haber process as a reversible reaction, 6.3.2 Conditions and rate in industrial equilibria, and 6.3.3 Fertilisers and the preparation of ammonium sulfate. Each one has a worked solution and a mark scheme showing where the marks go.