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 $\quad\quad\quad \frac{dx}{dt} = k\left[A\right]\left[B\right]$
it is second-order reaction
If $\quad \quad \quad \left(\frac{dx}{dt} \right)= k\left[A\right]$
or$\quad\quad\quad\quad= k \left[B\right]$
it is first order reaction.
Molecularity is independent of rate, but is the sum of the reacting substances thus it cannot be unimolecular reaction.