(a) A displacement reaction occurs when a more reactive ingredient displaces a less reactive element out of its compound. The displacement reaction involves both metals and non-metals.

An example of displacement reaction isw as follows:

CuSO₄ + Zn → ZnSO₄+ Cu

Here, Zinc being more reactive than Copper displaces it to form Zinc sulphate.

When two atoms or groups of atoms exchange places and form a new substance, this is known as a double displacement reaction. It usually takes place in watery solutions.

The following is an example of a double displacement reaction:

Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

In the reaction above, Sodium and Barium displace each other to give different products.

(b) A precipitation reaction occurs when an insoluble substance known as precipitate forms and separates out from a solution.

An example is when barium chloride solution is introduced to sodium sulphate solution, a white barium sulphate precipitate forms along with the sodium chloride solution.

Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl