CAIE A Level Chemistry 9701 · Equilibria
Agricultural soil is often treated with lime () to raise its pH. The carbonate–hydrogencarbonate buffer system in the soil is represented by:
A soil scientist adds a small amount of a strong acid, such as , to a sample of this soil. Suggest how the buffer system minimises the change in pH. In your answer, refer to the equilibrium above and to the conjugate acid–base pair involved.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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