Question

If a homogeneous catalytic reaction follows three alternative paths A, B and C, then which of the following indicates the relative rates with which the reaction moves?

• A. A > B > C
• B. C > B > A
• C. A > C > B
• D. A = B = C

Answer 1

The correct option is B C > B > A

Rate of a reaction is given by, $r=k[\text{reactant}{]}^{\text{order}}........(i)$
The value of rate constant, $k$, is given by Arrhenius equation:
$k=A{e}^{-\frac{E_a}{RT}}............\left(ii\right)$
So, from equations $\left(i\right)$ and $\left(ii\right)$, it is clear that rate is directely related to the value of $k$ which is inversely related to activation energy, $E_a$.
So, lower the activation energy, higher is the rate.
The activation energy in path A is maximum and hence it follows with lowest rate while in the path C, its rate is maximum due to its lowest activation energy.
Hence, (b) is correct.