Question

$K_a$ for $HA$ is $4.9\times {10}^{-8}$. After making the necessary approximation, calculate for its decimolar solution
(a) % dissociation
(b) $H^{+}$ ion concentration

Answer 1

$K_a=4.9\times {10}^{-8}$ $C=0.1M$

1)$\alpha =\sqrt{\frac{K_a}{C}}$=$7\times {10}^{-4}$

% dissociation=$100\times \alpha$=$7\times {10}^{-2}$

2)$HA\rightleftharpoons H^{+}+A^{-}$

$C(1-\alpha )$ $C\alpha$ $C\alpha$

$\left[H^{+}\right]$=$C\alpha$=$7\times {10}^{-5}M$