Calculate the pH of a 0.18 M solution of cyanide ion, CN- given the

Ka (HCN) = 6.2 x 10^-10.

I know how to calculate Ka and Kb values no problem, but I don't know which value to use in my calculations. Is it based on the conjugate base/acid formed or hydronium or hydroxide ions formed?

1 answer

I'm wondering, if Hydronium ions are formed , do we use Ka? And vice versa (OH- we use Kb?