Question

The factor which does not influence the rate of reaction is:

• A. nature of the reactants
• B. concentration of the reactants
• C. temperature
• D. molecular mass

Answer 1

The correct option is D molecular mass

The rate of the reaction is not influenced by molecular mass. However, it depends on the nature of reactants, the concentration of the reactants, order and temperature.

Consider a first order reaction: $aA\to bB$

The rate of the reaction $\left(r\right)=K[A{]}^{\alpha }$, where $\alpha$ is the order of the reaction and $K$ is the rate constant.

The rate expression is given by $K=A{e}^{(-Ea/RT)}$, where $R$ is the gas constant, $Ea$ is the activation energy and $T$ is the temperature.

Hence, the rate is independent of the molecular mass.