Question

Which of the following expressions is not applicable on the hydrolysis equilibrium ?

CN^– + H₂O $\rightleftharpoons$ HCN + OH^–

• A. $K_{h} = \frac{K_{w}}{K_{a}(HCN)}$
• B. $h = \sqrt{\frac{K_{h}}{C}}$
• C. $pH = \frac{1}{2}pK_{a}(HCN)$
• D. (H⁺) = $\sqrt{\frac{K_{w} \times K_{a}}{C}}$

Answer 1

Answer: (C)

$pH = \frac{1}{2}pK_{a}(HCN)$

Answer 2

For the salt of weak acid and strong base

pH = $\frac{1}{2}$ [pK_w + pK_a – log C]