(a) What is a chemical equation?

(b) Why is it necessary to balance a chemical equation?

(c) What are the limitations of a chemical equation?

(a) A chemical equation is the symbolic representation of a chemical reaction using symbols and formulae of the substances involved in the reaction.

(b) It is necessary to balance a chemical equation so as to make the number of atoms of the reactants equal to the number of atoms of the products because a chemical reaction is just a rearrangement of atoms and atoms are neither created nor destroyed during the chemical reaction.

(c) The limitations of a chemical equation are:

It does not inform about:

1. the physical states of the reactants and the products i.e. whether they are solids, liquids or gases.
2. the concentration of reactants and products.
3. the time taken for the completion of reaction.
4. the rate at which a reaction proceeds.
5. the heat changes during the reaction i.e. whether heat is given out or absorbed.
6. the conditions such as temperature, pressure, catalyst, etc. which affect the reaction.
7. the nature of the reaction i.e. whether it is reversible or irreversible.