Question

A reaction is first order in $A$ and second order in $B$ :
(i) Write differential rate equation.
(ii) How is the rate affected when the concentration of $B$ is tripled?
(iii) How is the rate affected when the concentration of both $A$ and $B$ is doubled?

Answer 1

It is given that a reaction is first order in $A$ and second order in $B$.

i) The differential rate equation is as follows:

Rate $=k\left[A\right][B{]}^2$
(ii) On increasing the concentration of $B$ three times, rate becomes $9$ times.
$\left(d\right[B]{)}^2=3^2=9$
(iii) When the concentrations of both $A$ and $B$ are doubled, rate becomes $8$ times.

$d\left[A\right]\left(d\right[B]{)}^2=2\times 2^2=8$