In which direction will the balance of hydrolysis of NaCN shift, if to the solution add: a) alkali; b) acid?

Sodium cyanide NaCN is a salt formed by a strong base NaOH and a weak acid HCN, as a result of which it hydrolyzes at the anion.

Let us write down the equation of hydrolysis with respect to the anion:

CN- + H2O = HCN + OH-

As can be seen from this equation, the solution alkalizes during hydrolysis.

Therefore, according to Le Chatelier’s principle, the addition of alkali to this solution a) will shift the equilibrium to the left, i.e. will slow down the hydrolysis, and the addition of b) acid, on the contrary, will shift the equilibrium to the right, i.e. will speed it up.