Chemistry 5070 · O Level · Fertilisers

Fertilisers — practice question

(a)[2]

State where the hydrogen and nitrogen used to manufacture ammonia by the Haber process come from.

(b)[3]

Ammonia is produced when aqueous ammonium sulfate is heated with sodium hydroxide. $(\text{NH}_4)_2\text{SO}_4 + 2\text{NaOH} \rightarrow 2\text{NH}_3 + \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$ A student adds $4.50\,\text{g}$ of sodium hydroxide to $50.0\,\text{cm}^3$ of $1.25\,\text{mol dm}^{-3}$ aqueous ammonium sulfate. Show by calculation that ammonium sulfate is in excess.

(c)[1]

When dilute sodium hydroxide is electrolysed, hydroxide ions are changed into oxygen and water at the anode. Construct the ionic equation for the reaction taking place at the anode.

(d)[1]

The first stage in the nitrate-ion test is to heat aluminium and sodium hydroxide with a solution containing nitrate ions. State the type of chemical reaction that takes place when a solution containing nitrate ions is heated with aluminium and sodium hydroxide.

(e)[3]

Nitrates from fertilisers cause eutrophication when they are washed out of soils into rivers. Describe the process of eutrophication.

Worked solution & mark scheme

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