Question

How can we define chemical equations.

Answer 1

A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactantentities are given on the left-hand side and the product entities on the right-hand side.
or
A chemical equation is a written representation of the process that occurs in a chemical reaction. A chemical equation is written with the reactants on the left side of an arrow and the products of the chemical reaction on the right side of the equation.The head of the arrow typically points toward the right or toward the product side of the equation, although reactions may indicate equilibrium with the reaction proceeding in both directions simultaneously.
The elements in an equation are denoted using their symbols. Coefficients next to the symbols indicate the stoichiometric numbers. Subscripts are used to indicate the number of atoms of an element present in a chemical species.
An example of a chemical equation may be seen in the combustion of methane:
CH4 + 2 O2 → CO2 + 2 H2O