Salt Preparation

So what is a salt?

A salt is the ionic compound formed when a metallic or ammonium ion partially or completely replaces the hydrogen ions of an acid. It contains a positive metal (or ammonium) ion from a base and a negative non-metal ion from an acid.

e.g. Ca(OH)2 + H2SO4 -> CaSO4 + 2H2O

Water of Crystallization

• Salt crystals are formed when salts combine with water molecules. These water molecules are known as water of crystallization. 
• Salts that contain water of crystallization are called hydrated salts.
• Water of crystallization can be removed from a salt when the hydrated salt is heated, leaving behind an anhydrous form of the salt.
• Anhydrous salts refer to salts that do not contain water of crystallization. They are often in the form of powders.

Solubility of Salts

Although salts are ionic compounds, not all salts are soluble in water. All Sodium, Potassium, Ammonium and Nitrate salts are soluble, all Chloride, Bromide and Iodide salts are soluble except for Silver and Lead (II) ones, all Sulfate salts are soluble except for Barium, Calcium and Lead (II) ones, all Carbonates are insoluble except for Sodium Carbonate, Potassium Carbonate and Ammonium Carbonate, and all Oxides and Hydroxides are insoluble except for Sodium, Potassium and Barium ones.

How to form insoluble salts

All insoluble salts can be prepared by precipitation. To precipitate an insoluble salt, mix solution A which contains the positive ions (cations) of the salt, and solution B which contains the negative ions (anions) of the salt. For example, Lead (II) Sulfate can be prepared using a soluble Lead (II) salt (such as Lead (II) Nitrate) and dilute sulfuric acid or any soluble sulfate.