Which is not true for a second order reaction?

Rate constant unit for the second order reaction ${\mathrm{mol}}^{-1}{\mathrm{L} \mathrm{s}}^{-1}$

${\mathrm{t}}_{1/2}\alpha {\mathrm{a}}^{1-\mathrm{n}}$ 

Here, $n=2$

$t_{1/2}\alpha a^{-1}$ 

This is Inversely Proportional to Half Life.

${\mathrm{t}}_{1/2}=\frac{1}{\mathrm{ak}}$

Here, initial concentration is a.

So, time to complete 75% reaction is twice for the 1st Order Reaction not for half life.