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AS · Practice questions · Sulfur dioxide and acid rain

Clean the smoke.

Six original Cambridge-style questions on sulfur dioxide, acid rain and its control.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

+4 in SO2, +6 in SO3 and H2SO4.

01
Recall
[3 marks]

Write equations to show how sulfur in coal leads to sulfuric acid in rain.

  • S + O2 → SO2. ✓
  • 2SO2 + O2 → 2SO3 (catalysed by NO2). ✓
  • SO3 + H2O → H2SO4. ✓
02
Recall
[2 marks]

Give two harmful effects of acid rain.

  • Damages limestone and marble buildings and statues. ✓
  • Lowers the pH of lakes, killing fish; damages trees by leaching nutrients from soil. ✓
03
Calculation
[2 marks]

Calculate the mass of SO2 produced when 500 tonnes of oil containing 3.00% sulfur by mass is burned. (Ar S 32.1; Mr SO2 64.1)

  • Mass of S = 0.0300 × 500 = 15.0 tonnes. ✓
  • Mass of SO2 = 15.0 × 64.1 ÷ 32.1 = 30.0 tonnes. ✓
04
Calculation
[2 marks]

Calculate the mass of calcium carbonate needed to absorb 32.0 kg of SO2 in a desulfurisation unit. (Mr: CaCO3 100.1, SO2 64.1)

  • n(SO2) = 32 000 ÷ 64.1 = 499 mol = n(CaCO3). ✓
  • Mass = 499 × 100.1 = 50 000 g = 50.0 kg. ✓
05
Explain
[2 marks]

Explain why sulfur dioxide is used in small amounts as a preservative in dried fruit.

  • It is an antioxidant, preventing the food from being oxidised and discoloured. ✓
  • It inhibits the growth of bacteria and fungi. ✓
06
Explain
[3 marks]

State the conditions of the Contact process and explain why a low pressure is used even though high pressure would increase the yield of SO3.

  • V2O5 catalyst, about 450 °C, 1 to 2 atm. ✓
  • The equilibrium already lies far to the right (about 99% conversion), so extra pressure gives little benefit. ✓
  • High-pressure equipment would be expensive. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.