Question

$t_{0.5}=constant,$ confirms the first order of the reaction as one $a^2{t}_{0.5}=constant$
confirms that the reaction is of order :

Answer 1

Given
$t_{\frac{1}{2}}\alpha \frac{1}{a^2}$
$\because t_{\frac{1}{2}}\alpha \frac{1}{a^{n-1}}$
$n-1=2$
$n=3$