The aim of this experiment is to prepare a pure sample of magnesium sulphate.
Making magnesium sulphate can be achieved in a number of ways. These include reacting an excess of magnesium or magnesium carbonate with sulphuric acid. An excess has to be used to make sure all the acid is used up. If any acid remained then the salt would be impure.
The fact that a gas is produced on reacting magnesium or magnesium carbonate with an acid allows us to tell when all the acid has been consumed. At this point no more bubbles of gas will appear and the excess magnesium or magnesium carbonate will remain as a solid in the reaction mixture.
