Hydrogen cyanide has the chemical formula HCN. The compound occurs as a colourless gas or a pale blue liquid. Its solution in water is called hydrocyqnic acid. it reacts with water as per the following reaction:

HCN (aq) + H20 (l) = CN- (aq) + H30 (aq)

what is the pH at equilibrium of 0.15 mol/L solution of HCN if hydrocyanic acid has a ka of 6.2 x 10^-10