Question

The $pOH$ of ${10}^{-8}MHCl$ is :

• A. 8
• B. 6
• C. between 6 and 7
• D. between 7 and 8

Answer 1

The correct option is D between 7 and 8

$\left[H^{+}\right]$ from $HCl$ = ${10}^{-8}M$
$\left[H^{+}\right]$ from $H_{2}O$ = ${10}^{-7}M$
total $\left[H^{+}\right]=({10}^{-8}+{10}^{-7})=1.1\times {10}^{-7}M$
we know that $pH=-lo{g}_{10}\left[H^{+}\right]$
$pH=-lo{g}_{10}(1.1\times {10}^{-7})=7-0.0414=6.9$
Also, $pH+pOH=14$
$6.9+pOH=14$
$pOH=14-6.9=7.1$
hence, $pOH$ of ${10}^{-8}MHCl$ is between 7 and 8