A 1000 mL solution is composed of 0150 M hydrocyanic acid HC

A 100.0 mL solution is composed of 0.150 M hydrocyanic acid (HCN) and 0.150 M sodium cyanide (NaCN). Determine the pH of this solution. Can you please show how you got the answer? Thanks.

4.9 x 10^-10 = x^2 / 0.025-x
x = 3.5 x 10^-6 = [H+]
pH = 5.46

[H+]=4.76*10^-10.
pH=-log[H+] = -log(4.76*10^-10) = 9.32.