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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 is used because it increases the reaction rate, allowing the reaction to proceed faster. However, since the forward reaction is exothermic, using too high a temperature would decrease the yield of sulfur trioxide (SO₃). Therefore, a balance is achieved by selecting a moderately high temperature as a compromise to ensure both sufficient yield and reaction rate.
Step 2
Explain why you would expect this reaction to be carried out at high pressure.
Answer
This reaction is expected to be carried out at high pressure because high pressure increases the yield of products. Since there are more moles of gas on the left-hand side (LHS) of the reaction, increasing the pressure shifts the equilibrium to the right, favoring the formation of sulfur trioxide (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 magnesium sulfate, a white precipitate forms, indicating the presence of magnesium ions. In contrast, when sodium hydroxide is added to aluminium sulfate, the precipitate dissolves in excess sodium hydroxide due to the formation of soluble aluminate ions. This difference helps distinguish between the two solutions.