(a) The unit $\mathrm{L}{\mathrm{mol}}^{-1}{\mathrm{}\mathit{s}\mathit{e}\mathit{c}}^{-1}$ for rate constant is the unit of second order reaction.
(b) For reaction $\mathrm{A}\to \mathrm{B}$,
Rate of reaction $\left(\mathit{r}\right)$
$=\mathit{k}{\left[\mathrm{A}\right]}^2.....1$
If the concentration of reactant increased to three times.
Rate of reaction $\left({\mathit{r}}^{\prime }\right)$
$=\mathit{k}{\left[3\mathrm{A}\right]}^2.....2$
Thus, on dividing eq. 1 and 2 .
$\frac{\mathit{r}}{{\mathit{r}}^{\prime }}=\frac{\mathit{k}{\left[\mathrm{A}\right]}^2}{\mathit{k}{\left[3\mathrm{A}\right]}^2}$
$=\frac{1}{9}$
Therefore, rate of formation of B increases to nine times.
(c) Integrated rate equation for zero order reaction is
$\mathit{k}=\frac{\left[{\mathrm{R}}_0-\mathrm{R}\right]}{\mathit{t}}$
Where, $\mathit{k}=$ rate constant