A solution is prepared by dissolving 0.23 mol of hydrocyanic acid and 0.24 mol of sodium cyanide in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of NaOH to this buffer solution causes the pH to increase slightly. The pH does not increase drastically because the NaOH reacts with the present in the buffer solution. The Ka of hydrocyanic acid is 4.9 × 10^-10.

A. cyanide

B. H2O

C. hydrocyanic acid

D. H3O+

E. This is a buffer solution: the pH does not change upon addition of acid or base.