Define the term 'order of reaction' for chemical reactions.

Explanation

Order of a chemical reaction : The order of a chemical reacation is defined as the sum of the powers (or exponents ) to which the concentration terms of the reactants are raised in the rate law expression for the given reaction.
Explanation.
Consider a reaction,
`n_(1) A+ n_(2)B to` Product
Where `n_(1)` moles of A react with `n_(2)` moles of B.
The rate of this reaction can be expressed by the reaction , hence the order of the reaction is .
`n = n_(1) + n_(2)` , ( observed ,experimentally).
If n = 1 , the reactions is called the fist order reaction , if n = 2 , it is called the second order reaction, etc.
If n = 0 , it is called the zero order reaction , e.g., photochemical reaction of `H_(2(g))` and `Cl_(2(g))`