A salt is a compound formed when the hydrogen of an acid is replaced by a metal. If the hydrogen is replaced partially (i.e. there is hydrogen in the salt), this is called an acid salt. However, these can only be formed when the basicity of the acid is 2 or more. Salts are always bonded ionically, and are composed of a cation and an anion. These are in a ratio such that the overall charge is neutral.
Preparation of salts[edit | edit source]
Titration[edit | edit source]
This method is used when adding an acid to a dissolved base (usually a hydroxide).
Precipitation[edit | edit source]
This is used to make insoluble salts. Two soluble salts are mixed, giving the products as a soluble and insoluble salt. The solubility of all salts must be checked before in order to make sure the reactants are soluble.
Neutralisation[edit | edit source]
This is where an acid is neutralised by an excess solid. The solid is either a metal, a metal oxide or a metal carbonate.
Preparation of Acid Salts[edit | edit source]
This is done by titration. However, to form an acid salt, exactly double the volume of acid is needed to produce an acid salt, compared to a normal salt. For example, with sodium hydroxide and sulphuric acid, if 25cm3 sulphuric acid is needed to form sodium sulphate; then 50cm3 is needed to form the acid salt, sodium hydrogensulphate.