Chemistry 5070 · O Level · Fertilisers

Fertilisers — practice question

Concentrated aqueous ammonia is used in the manufacture of fertilisers such as ammonium phosphate, $(\text{NH}_4)_3\text{PO}_4$.
(a)[2]

Calculate the percentage by mass of nitrogen in ammonium phosphate.

(b)[1]

Explain the reason farmers apply nitrogen-containing fertilisers to their fields.

(c)[2]

Describe a test used for ammonia and state the result.

(d)[2]

Explain why applying calcium hydroxide to the soil at the same time as ammonium phosphate causes nitrogen to be lost from the soil.

(e)[3]

Calculate the concentration, in $\text{mol/dm}^3$, for the aqueous ammonia.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Nitrogen percentage = (3\times14 / 149) \times 100 = 28.2%

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