1.What does a fertiliser contain to make plants grow?

2. How do they get into the plant?

3. Suggest the properties a fertiliser must have.

Plants absorb minerals through their roots

Soil particles

N

K

K

P

rock sulphuric super phosphate

phosphate acid(insoluble) (soluble)

Rock phosphate (calcium phosphate) is insoluble. By reacting it with sulphuric acid converts it to a more soluble form (super phosphate).

Making Fertiliser

Fertilisers containing nitrogen are vital for the healthy growth of plants. One of the commonest nitrogen compounds is the gas ammonia (NH3). In this experiment you will make a solid fertiliser, ammonium sulphate, by reacting sulphuric acid with ammonia solution.

2NH3(aq) H2SO4(aq) (NH4)2SO4(aq)

Analysis 1 Write a word equation for the reaction that has

taken place.2 What type of reaction takes place when an acid

reacts with an alkali?3 Before you started heating, did the mixture

contain excess acid or excess ammonia?4 What happened to this excess when you heated

the mixture?5 Why would it have been a greater safety hazard if

you had evaporated the mixture when the pH was still below 7?

6 If you carry on heating until all the water has boiled away:a what safety hazard(s) might be introducedb how would the product look different from the crystals that can be formed?