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

Ans:
Balanced Chemical Equation is an equation in which the total number of atoms of each element in the reactants,on the left side of the equation,is the same as the number of atoms in the products formed, on the right side of the equation.

Why should Chemical Equation be balanced?

An equation must be balanced in order to comply with the "Law of Conservation of Matter",which states that matter is created nor destroyed in the course of a chemical reaction.
An unbalanced equation would imply that atoms have been created or destroyed.
Example :

$$ Zn +H_{2}SO4 \rightarrow ZnSO_{4} + H_{2}$$

Element Name	In Reactants	In Products
No. of Zn atoms	1	1
No.of H atoms	2	2
No.of S atoms	1	1
No.of O atoms	4	4

Thus above reaction between zinc and dilute sulphuric acid is a balanced equation.