CAIE A Level Chemistry 9701 · Equilibria
A farmer adds a sparingly soluble calcium compound to acidic soil to raise its pH. The compound reacts with hydrogen ions, and the resulting solution contains both a weak acid and its conjugate base, so it acts as a buffer.
Suggest and explain how this buffer solution is formed and how it controls the pH of the soil.
6 marks, so the mark scheme is looking for about 6 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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