What this practice covers
These questions are drawn from past CIE 9701 Chemistry papers and filtered to equilibria. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
Start practising practice questions →
What examiners see students get wrong here
These are the errors that cost marks on equilibria, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Identifying a conjugate pair that differs by more than one proton, such as H₂SO₄ and SO₄²⁻.
- Saying pure water always has pH 7. It does at 298 K, and it is neutral at every temperature, but the pH changes with temperature.
- Taking -log of a hydroxide concentration and calling it the pH.
- Forgetting to double the concentration for a strong diprotic acid.
- Treating a weak acid as fully dissociated, so [H⁺] is taken as the acid concentration.
- Forgetting the square root in [H⁺] = √(K_a[HA]).
- Reading a larger pK_a as a stronger acid. Larger K_a means stronger, so larger pK_a means weaker.
- Describing a buffer as a solution that keeps the pH constant. It resists change.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Equilibria revision notes.