Question

It was determined that the chemical reaction $A+B\to C$ is first-order with respect to $A$ and first-order with respect to $B$. Assuming the reaction to be an elementary process, which of the following statements is true concerning this reaction?

• A. The molecularity and overall order are both $1$.
• B. The molecularity is $1$, while the overall order is $2$.
• C. The molecularity is $2$, while the overall order is $1$.
• D. The molecularity and overall order are both $2$.

Answer 1

The correct option is D The molecularity and overall order are both $2$.

$A+B⟶C$

$Rate=K\left[A\right]\left[B\right]$ (Since, it is first order with respect to both $A$ and $B$)

$\therefore$Overall order= Order with respect to $A$ + order with respect to $B$

$=1+1$

Overall order$=2$

Also, $1$ molecule of $A$ & $1$ molecule of $B$ are taking part in the reaction.

Therefore, molecularity$=1+1=2$