Acid/Base Equilibrium for NaCN?

Question

Hi there! I'm not very strong chemistry-wise, & I'm having a few issues with this question - please help!

It reads:

The pH of 0.100M NaCN is 11.2

a) Write the net ionic equation for the acid/base equilibrium

b) Calculate the [OH-] in the solution

c) Calculate the % hydrolysis of the CN- ion in this solution

Thanks so much!

Answer 1

Na is a spectator ion so we have

CN- + H2O <--> HCN + OH-

pH + pOH = 14

14 - pH = pOH = 2.8

[OH-] = 10^(-pOH) = 0.0066069345M

My guess for the last one...

% hydrolysis = (0.0066069345/2.8)*100% = 0.236%

[Answer: see above]