Farmers use fertilisers to increase the yield of their crops.
Diammonium phosphate, (NH4)2HPO4\mathrm{(NH_{4})_{2}HPO_{4}}(NH4)2HPO4, is a fertiliser. It is made by reacting ammonia with phosphoric acid.
ammonia + phosphoric acid → \rightarrow\,→ diammonium phosphate
Name the three elements, in compounds, that are most important in fertilisers.
Calculate the percentage by mass of nitrogen in diammonium phosphate, (NH4)2HPO4\mathrm{(NH_{4})_{2}HPO_{4}}(NH4)2HPO4.
Use the equation: percentage of nitrogen = (total Ar of the nitrogen atoms ÷ Mr of the compound) × 100
Relative atomic mass (Ar): H = 1.0, N = 14.0, O = 16.0, P = 31.0
Give your answer to 3 significant figures.
Percentage of nitrogen = ...... %
The ammonia used to make diammonium phosphate is made by the Haber process.
Explain why the Haber process is important for producing enough food.
The table compares how diammonium phosphate is made in a school laboratory and in industry.
| Feature | Laboratory preparation | Industrial production |
|---|---|---|
| mass made | about 20 g | about 3000 tonnes per day |
| source of ammonia | bottle of ammonia solution | made on site by the Haber process, from nitrogen in the air and hydrogen from natural gas |
| source of phosphoric acid | bottle of phosphoric acid | made on site by reacting phosphate rock with sulfuric acid |
| how the reactants are mixed | ammonia solution added to the acid from a burette, using an indicator | ammonia and acid fed into a large reactor all the time |
| how the solid is obtained | solution heated to evaporate water, then left to crystallise | water evaporated using heat given out by the reaction; solid made into small pellets |
| how long it runs | one batch, a few hours | non-stop, day and night |
Compare the laboratory preparation of diammonium phosphate with its industrial production.
Use the information in the table and your own knowledge. Explain the reasons for the differences.
61 exam-style questions on OCR GCSE Chemistry 6.1 Improving processes and products, covering 6.1.1 Extracting metals industrially and by electrolysis, 6.1.2 Life cycle assessment and recycling, 6.1.3 Biological methods of metal extraction, 6.1.4 The Haber process and the production of fertilisers, 6.1.5 Alloys and their uses, 6.1.6 Corrosion and its prevention, 6.1.7 Comparing and selecting materials, and 6.1.8 Industrial conditions, rate and position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.