Question

$K_a$ for ascorbic acid, $HAsc,$ is $5\times {10}^{-5}$. Calculate the hydrogen ion concentration and percentage hydrolysis in an aqueous solution in which the concentration of ${Asc}^{-}$ ions is $0.02M$.

Answer 1

Degree of hydrolysis $h=\sqrt{\frac{K_w}{C{K}_a}}$
$=\sqrt{\frac{{10}^{-14}}{0.02\times 5\times {10}^{-5}}}={10}^{-4}$
% hydrolysis $=0.01$
$pH=\frac{1}{2}[p{K}_w+p{K}_a+\log C]$
$=\frac{1}{2}[14+(-\log 5\times {10}^{-5})+\log 0.02]=8.3$
$\left[H^{+}\right]=5\times {10}^{-9}M$