Question

A reaction involving two different reactants can never be

• A. bimolecular reaction
• B. second order reaction
• C. first order reaction
• D. unimolecular reaction

Answer 1

Answer: (D)

There are two different reactants (say A and B).
$A+B\to$ product
Thus it is a bimolecular reaction.
If $\frac{dx}{dt}=k\left[A\right]\left[B\right]$
it is second-order reaction
If $\left(\frac{dx}{dt}\right)=k\left[A\right]$
or$=k\left[B\right]$
it is first order reaction.
Molecularity is independent of rate, but is the sum of the reacting substances thus it cannot be unimolecular reaction.