Chemistry 5070 · O Level · Fertilisers

Fertilisers — practice question

This item concerns ammonium sulfate, $(\text{NH}_4)_2\text{SO}_4$.
(a)[1]

Explain why farmers apply fertilisers to soil used for crop growth.

(b)[2]

Explain why farmers avoid adding calcium hydroxide to the soil straight after ammonium sulfate has been added.

(c)[3]

Calculate the percentage by mass of nitrogen in ammonium sulfate. Give your answer correct to three significant figures.

(d)[2]

Complete the equation for the reaction between ammonium sulfate and aqueous sodium hydroxide. $(\text{NH}_4)_2\text{SO}_4 + 2\text{NaOH} \rightarrow \ldots + \ldots + \ldots$

(e)[2]

Ammonium sulfate breaks down when heated. The reaction is endothermic. $3(\text{NH}_4)_2\text{SO}_4 \rightarrow 4\text{NH}_3 + 3\text{SO}_2 + \text{N}_2 + 6\text{H}_2\text{O}$ Finish and label the energy profile diagram for this reaction so that it shows the reactants, products and the enthalpy change of the reaction.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Raise crop yield / boost plant growth / replace minerals lost when crops are harvested

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