Chemistry 5070 · O Level · Fertilisers

Fertilisers — practice question

This question concerns ammonia and ammonium salts.
(a(i))[1]

Name the catalyst that is used in the Haber process.

(a(ii))[1]

Explain how a catalyst increases the rate of reaction.

(b)[3]

Ammonium phosphate, $(\text{NH}_4)_3\text{PO}_4$, is used as a fertiliser. Calculate the percentage by mass of nitrogen in ammonium phosphate. Give your answer to three significant figures.

(c(i))[1]

State the name of a compound used to reduce the acidity of soil.

(c(ii))[1]

Explain how this compound reduces the acidity of soil.

(d)[2]

Ammonia is produced when nitrogen(I) oxide, $\text{N}_2\text{O}$, is reduced by hydrogen. The reaction is exothermic. $\text{N}_2\text{O} + 4\text{H}_2 \rightarrow 2\text{NH}_3 + \text{H}_2\text{O}$ Complete and label the energy profile diagram for this reaction so that it includes: • the reactants and products • the enthalpy change of the reaction.

(e)[2]

Copper(II) oxide, $\text{CuO}$, reacts with ammonia. The products are copper, nitrogen and a liquid which turns blue cobalt(II) chloride paper pink. Construct the equation for this reaction.

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