For N2O4(g) <=> 2NO2(g), the equilibrium partial pressures are p(N2O4) = 40 kPa and p(NO2) = 60 kPa. Calculate Kp and its unit.
[3 marks]
Total for this question: 3
All calculations
Equilibrium constant Kp
Physical chemistry
AQA 7405
ORIGINAL
Kp = product partial pressures / reactant partial pressures
Only gaseous species appear, and every partial pressure is raised to its equation coefficient.
Board and spec code confirmed against AQA 7405 · registry checked 2026-07-11How this checking works
Work it, then mark it
Do each calculation on paper first, then reveal the mark scheme and tick the marks you actually earned — the same way you should mark past papers.
Q1
Do the calculation on paper first — then mark it.
Where the marks get lost
- Forgetting to square the NO2 partial pressure.
- Assuming Kp is unitless without cancelling pressure powers.
Exam tip: Derive the unit from total product powers minus total reactant powers after writing the expression.
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