Q81 · Practice questionComplex familiar6 marks
QUESTION 81 (6 marks)
In the contact process, . A feed contains 8.00 mol SO₂ and 3.00 mol O₂.
a) Identify the limiting reagent and calculate the theoretical SO₃ amount. [3 marks]
b) The actual SO₃ amount is 4.80 mol. Calculate percentage yield. [1 marks]
c) Explain how increasing pressure affects equilibrium yield. [2 marks]
WORKED SOLUTION
6 marksPractice marking scheme
O₂ is limiting; theoretical SO₃ = 6.00 mol; yield = 80.0%; compression favours SO₃.
Eight moles SO₂ would need four moles O₂, exceeding supply. Three moles O₂ produce six moles SO₃. Actual/theoretical ×100 =80.0%. The product side has two gas moles versus three on the reactant side.
- Compares stoichiometric reagent amounts. [1 marks]
- Identifies O₂ as limiting. [1 marks]
- Calculates theoretical 6.00 mol SO₃. [1 marks]
- Calculates 80.0% yield. [1 marks]
- Predicts higher equilibrium SO₃ yield with pressure. [1 marks]
- Uses fewer product gas moles to justify. [1 marks]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusHow many marks did you earn?
Compare your working with the guide above.