Salt

• A compound formed in the reaction between an acid and a base is called Salt.

Properties of Salts:

• Some of the characteristic properties of salts are:

Melting and boiling points:

• Salts are mostly solids which melt as well as boil at high temperatures.

Solubility in water:

• Salts are generally soluble in water but some salts are insoluble also.

For example, sodium chloride, potassium sulphate, aluminum nitrate, ammonium carbonate etc., are soluble salts.

Silver chloride, lead chloride, copper carbonate, etc., are insoluble in water.

Water of crystallization:

• Generally, salts are found as crystals with water molecules present in them. This water is called water of crystallization and such salts are called hydrated salts.

For example

• Copper sulphate crystal contains five molecules of water per molecule.
• The formula is CuSO₄.5H₂O. This water of crystallization gives the crystal its shape.
• Water of crystallization also gives colour to some crystals.
• On heating, hydrated salts lose their water of crystallization and as a result, of which the crystals lose their shape and colour and change to a powdery substance.
• The hydrated salts that have lost their water of crystallization are called anhydrous salts.
• When hydrated copper sulphate is heated, it gives out water molecules to form white powdery anhydrous copper sulphate, which on addition of water again converts to hydrated copper sulphate.