According to Law of conservation of matter,"matter can neither be created nor destroyed during a chemical reaction". Therefore this law is very important in a chemical equation. A chemical equation must be balanced to obey this law. Means, the mass of the reactant must equals the mass of products.
For example,
C + O₂ ---------> CO₂
12g + 32g ---------> 44g
In this reaction the total mass of reactant (44g) is exactly equal to the mass of product (44g).
So, keeping the law of conservation of matter it is important to have a balanced chemical equations.
