(a) Explain the following terms :
(i) Order of a reaction
(ii) Molecularity of a reaction
(b) The rate of a reaction increases four times when the temperature changes from 300 K to 320 K. Calculate the energy of activation of the reaction, assuming that it does not change with temperature. `(R = 8.314 J K^(-1) mol^(-1))`

Explanation

### Step-by-Step Solution

#### (a) Explanation of Terms

**(i) Order of a Reaction:**
The order of a reaction is defined as the sum of the powers of the concentration terms in the rate law expression for that reaction. It indicates how the rate of reaction depends on the concentration of the reactants. For example, if the rate law for a reaction is given by:
\[ \text{Rate} = k[A]^m[B]^n \]
where \( [A] \) and \( [B] \) are the concentrations of the reactants, and \( m \) and \( n \) are their respective orders, then the overall order of the reaction is \( m + n \).
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