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This question is about sulfuric acid and sulfates - AQA - GCSE Chemistry - Question 5 - 2017 - Paper 3
Question 5
This question is about sulfuric acid and sulfates. One reaction in the industrial production of sulfuric acid is: $$2SO_2 (g) + O_2 (g) \rightleftharpoons 2SO_3 (g... show full transcript
Worked Solution & Example Answer:This question is about sulfuric acid and sulfates - AQA - GCSE Chemistry - Question 5 - 2017 - Paper 3
Step 1
Explain why a moderately high temperature, instead of a low temperature, is used for this reaction.
Answer
A moderately high temperature increases the reaction rate, allowing the reaction to occur more quickly. However, it does reduce the yield of SO₃. Since the forward reaction is exothermic, a low temperature would favor the production of reactants. Therefore, a compromise temperature is chosen to balance the rate of reaction and the yield.
Step 2
Explain why you would expect this reaction to be carried out at high pressure.
Answer
High pressure increases the yield of the reaction because it shifts the equilibrium to the right, towards the product side. This is due to the fact that there are more moles of gas on the left-hand side (2 moles of SO₂ and 1 mole of O₂) compared to the product side (2 moles of SO₃).
Step 3
Step 4
Describe how sodium hydroxide solution is used to distinguish between a solution of magnesium sulfate and a solution of aluminium sulfate.
Answer
When sodium hydroxide solution is added to a solution of aluminium sulfate, a white precipitate forms that dissolves in excess sodium hydroxide. In contrast, when added to magnesium sulfate, a white precipitate forms that does not dissolve in excess sodium hydroxide. This difference allows for the identification of the two sulfates.