Question

Explain the rate of reaction. Describe the order of reaction with example.

Hint:

Molecularity is theoretical and whole number, while order is experimental and may be fractional or zero. Always check experimental data to find order of reaction.

Answer 1

Rate of reaction:
The rate of reaction is defined as the change in concentration of a reactant or product per unit time.
\[ \text{Rate} = -\frac{d[\text{Reactant}]}{dt} = \frac{d[\text{Product}]}{dt} \]
Order of reaction:
The order of a reaction is the sum of the powers of the concentration terms of reactants in the experimentally determined rate law.
For a reaction:
\[ aA + bB \;\rightarrow\; Products \]
Rate law is:
\[ r = k[A]^x[B]^y \]
Here, order of reaction = \(x+y\).
Examples:
1. First-order reaction: Decomposition of H$_2$O$_2$ \[ 2H_2O_2 \;\rightarrow\; 2H_2O + O_2 \] Rate = $k[H_2O_2]$, order = 1.
2. Second-order reaction: Saponification of ester with NaOH Rate = $k[\text{Ester}][\text{NaOH}]$, order = 2.
\[ \boxed{\text{Order is always determined experimentally and can be 0, fractional, or whole.}} \]