Question

The $pH$ of 0.1 M solution of cyanic acid ($HCNO$) is 2.34. Calculate the ionization constant of the acid and its degree of ionization in the solution.

Answer 1

$PH=-log\left[H^{+}\right]$

Hence, $\left[H^{+}\right]={10}^{-pH}$

$\left[H^{+}\right]={10}^{-2.34}=4.57\times {10}^{-3}M=\left[CN{O}^{-}\right]$

$K_a=\frac{\left[H^{+}\right]\left[CN{O}^{-}\right]}{\left[HCNO\right]}=\frac{(4.57\times {10}^{-3})(4.57\times {10}^{-3})}{0.1}=2.09\times {10}^{-4}$

The degree of dissociation = $\sqrt{\frac{K_a}{c}}=\sqrt{\frac{2.09\times {10}^{-4}}{0.1}}=4.57\times {10}^{-2}$