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AS · Practice questions · Nitrogen oxides and pollution

Exhaust to atmosphere.

Six original Cambridge-style questions on nitrogen oxides and nitrogen pollution.

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.
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Made hot, removed by catalysts, regenerated in air.

01
Explain
[2 marks]

Explain why NO forms in a car engine but not in the atmosphere at ordinary temperatures.

  • The N≡N bond is very strong, so the reaction N2 + O2 → 2NO has a very high activation energy. ✓
  • Only the very high temperatures in the engine (or lightning) provide enough energy. ✓
02
Recall
[2 marks]

Write equations to show how NO2 catalyses the oxidation of SO2 in the atmosphere.

  • SO2 + NO2 → SO3 + NO. ✓
  • NO + ½O2 → NO2 (NO2 regenerated). ✓
03
Analysis
[2 marks]

Use oxidation numbers to show that the reaction 2CO + 2NO → 2CO2 + N2 is a redox reaction.

  • C: +2 in CO to +4 in CO2 (oxidised). ✓
  • N: +2 in NO to 0 in N2 (reduced). ✓
04
Explain
[3 marks]

Describe how the use of nitrate fertilisers can lead to the death of fish in a lake.

  • Nitrates are washed (leached) from fields into the lake. ✓
  • Algae grow rapidly and block light, so plants below die. ✓
  • Bacteria decomposing the dead material use up dissolved oxygen, so fish suffocate. ✓
05
Recall
[2 marks]

Name the substances that react to form photochemical smog and one harmful product.

  • Nitrogen oxides and unburnt hydrocarbons, in sunlight. ✓
  • Products include peroxyacetyl nitrate (PAN) and ozone. ✓
06
Recall
[1 marks]

Write an equation for the formation of nitric acid from NO2, oxygen and water.

  • 4NO2 + O2 + 2H2O → 4HNO3. ✓

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.