Chemistry 5070 · O Level · Fertilisers

Fertilisers — practice question

Farmers make use of some calcium compounds.
(a)[1]

Calcium hydroxide dissolves in water to make limewater. If carbon dioxide is bubbled through limewater, a white precipitate of calcium carbonate appears. Write the equation for this reaction.

(b)[2]

Calcium hydroxide is used to neutralise acidic soils. Explain, using an ionic equation, why calcium hydroxide is able to neutralise acidic soils.

(c)[2]

A farmer applies ammonium nitrate as a fertiliser to an acidic soil. He then adds calcium hydroxide to neutralise the acidic soil. Explain one disadvantage of using calcium hydroxide to neutralise this acidic soil.

(d)[4]

The farmer uses a different fertiliser. This fertiliser has the following percentage composition by mass: Ca, 17.1%; H, 1.7%; P, 26.5%; O, 54.7%. Calculate the empirical formula of this compound and suggest the formula of the anion present in the fertiliser.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Balanced equation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

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