Neutralisation is the reaction of an acid with an alkali or a base to form a salt and water: acid + alkali → salt + water, and acid + base → salt + water. For example, hydrochloric acid and sodium hydroxide form sodium chloride and water. The first part of the salt's name comes from the metal in the alkali or base. The second part comes from the acid: hydrochloric acid makes chlorides, sulfuric acid makes sulfates and nitric acid makes nitrates.
A pure dry sample of a salt can be made from an acid and an insoluble base such as copper oxide. Add the base to warm dilute sulfuric acid a little at a time, stirring, until no more dissolves. The excess solid shows that all the acid has reacted. Remove the excess copper oxide by filtering. The solution that passes through, the filtrate, is copper sulfate solution.
Heat the filtrate gently to evaporate some of the water until crystals just start to form, then leave it to cool so that crystals grow. Filter off the crystals, wash them with a little cold distilled water and dry them between sheets of filter paper. This gives a pure dry sample of copper sulfate.
