The $P^H$  of 1.2% (w/v) aqueous solution of $C{H}_{3}COOH$  at ${25}^{0}C$  is ($P^{K_a}$ = 4.7)

$\left[C{H}_{3}COOH\right]=\frac{1.2}{60}\times \frac{1000}{100}=0.2M$

$P^H=\frac{1}{2}{P}^{K_a}-\frac{1}{2}\log c$

        $=\frac{1}{2}\left(4.7\right)-\frac{1}{2}\log \left(0.2\right)$

        $=2.7$