Salts

Essentials

A salt is a substance produced when the hydrogen in an acid is replaced by a metal.
This replacement can occur through various reactions including neutralisation, reaction with metals or reaction with bases.
Salts are generally crystalline solids and can be colourless or coloured depending on the presence of certain ions.

Formation of Salts

Neutralisation is a chemical reaction between an acid and a base occurring when their respective effects are balanced out to produce a salt and water.
- The general formula for a neutralisation reaction is: Acid + Base -> Salt + Water.
A metal can displace hydrogen from an acid, forming a salt, in a redox reaction due to the metal’s reactivity.
- The general equation is: Acid + Metal -> Salt + Hydrogen gas.
A base can also react with an acid to produce a salt and water in what’s often called an ‘acid-base’ or ‘neutralisation’ reaction.
- The formula is: Acid + Base -> Salt + Water.

Types of Salts

Soluble salts are those that dissolve in water. These include all nitrates, most sulfates (except barium and lead sulfate), and common salts of sodium, potassium and ammonium.
Insoluble salts do not dissolve in water. These include most carbonates and phosphates, and some sulfates (barium and lead sulfate).
Depending on the acid used in formation, different types of salts like chlorides, sulfates, nitrates or carbonates can be formed.

Properties of Salts

Salts typically have high melting and boiling points due to strong ionic bonds.
Many salts are soluble in water, forming neutral solutions unless the salt is the product of a weak acid or base, in which case the solution will be slightly acidic or basic.
Salts can conduct electricity when molten or in solution, as their ions are free to move and carry charge.

Uses of Salts

Salts have a wide range of uses depending on their specific properties.
Sodium chloride (table salt) is used for seasoning food, in water softening, and in many industrial applications.
Potassium nitrate (saltpetre) is used in fertilisers and fireworks.
Copper sulfate is a fungicide used in agriculture and horticulture.
Some salts are used in bath products for their therapeutic properties.