Preparation of Salts

Section: Preparation of Soluble Salts

Soluble salts can be prepared through multiple methods including reaction of a metal with an acid, reaction of a base with an acid, or reaction of a carbonate with an acid.
The general equation for these reactions involves the reactants (metal, base, or carbonate and an acid) reacting to produce a salt and other by-products such as hydrogen or water.
A specific soluble salt, for example, can be prepared by reacting a suitable insoluble base or metal with an acid, then allowing the salt to crystallise out of the solution as it cools.

Section: Preparation of Insoluble Salts

Insoluble salts are often prepared through a precipitation reaction, where two soluble salts in aqueous solution mix to form an insoluble salt.
This process can be predicted using solubility rules to determine which salts formed will be insoluble.
After the reaction takes place, the insoluble salt is often left as a precipitate and can be separated out via filtration.

Section: Preparation of Salts by Neutralisation

Another common method of preparing salts is through a neutralisation reaction, where an acid reacts with a base to form a salt and water.
This method involves first selecting an appropriate acid and base pair, which will give the desired salt.
The acid and base are mixed together until the solution is neutralised, then the solution is evaporated to leave behind the desired salt.
Indicators such as litmus can be used to determine when all the acid or base has reacted and the solution is neutral.

Section: Crystallisation of Salts

After a salt has been prepared, the solution often needs to be crystallised to isolate the salt.
Crystallisation is a physical process that involves removing the liquid from a solution to leave behind the dissolved salt.
The solution can be carefully heated to evaporate water, until the point where the solution is saturated and begins to crystallise.
The crystals of salt can then be collected and dried, resulting in the final, pure salt product.