Chemical Changes: Making Insoluble and Soluble Salts

Insoluble salts are created through a process called precipitation, which occurs when two solutions combine to create an insoluble solid, or precipitate.
By contrast, soluble salts are generated through the neutralisation of acids and bases, or the reaction of acids with carbonates.
In precipitation reactions, two soluble salts combine to create an insoluble salt. For example, lead nitrate and sodium chloride can combine to form lead chloride, which is insoluble, and sodium nitrate.
An insoluble salt can also be made by mixing two solutions of soluble salts. This process is called the ‘double decomposition’, as the ions of the two soluble salts are swapped.
In neutralisation, an acid and an alkali react to produce a salt and water. For instance, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride and water.
Acid-base reactions are also called neutralisation reactions, denoting that the acid and base effectively cancel each other out to produce water and a salt.
An acid can react with a metal carbonate, like calcium carbonate, to produce a salt (calcium chloride), water and carbon dioxide.
To produce a crystal of a soluble salt from a solution, it should be left to evaporate. Salt crystals will form as the water evaporates.
Filtration and crystallisation are often utilised to separate a salt from an aqueous mixture.
The pH of a solution can be controlled by a process called “titration,” in which an acid-base reaction takes place. This process is important in producing soluble salts.
Some examples of commonly produced soluble salts include sodium chloride, potassium nitrate and ammonium chloride. Insoluble salts often include substances like silver chloride, lead sulphate and barium carbonate.
To check if a salt is soluble or insoluble, a solubility chart can be used. Most nitrates are soluble, while most carbonates and phosphates are not.