What is a balanced chemical equation? Why should chemical equations be balanced?

The method of representing a chemical reaction with the help of symbols and formulae of substances involved is called a chemical equation.  The '+' is read as 'reacts with' and the arrow '' means 'produces'. The chemical formulas on the left represent the starting substances, called reactants.

Example: Zinc metal reacts with dilute sulphuric acid to form zinc sulphate and hydrogen gas.

This equation is written as:$Zn\ ( s) \ +\ H_{2} SO_{4} \ ( aq) \ \rightarrow \ ZnSO_{4} \ ( aq) \ +\ H_{2} \ ( g) +Heat$

A balanced chemical equation has the number of atoms of each element equal on both the left and right sides of the reaction. It has equal masses of various elements in the reactants and products.

Example: $Ca( OH)_{2} \ ( aq) \ +CO_{2\ }( g) \ \rightarrow \ CaCO_{3} \ ( s) \ +\ H_{2} O\ ( l)$

A chemical equation should be balanced to satisfy the law of conservation of chemical reactions.