what is the pH of a 2.62x10^-1 M NaNO2 solution? NB the pKa for HCN=9.212

Question

12.13
13.42
1.87
8.29
0.58
and also; what is the pH of a 2.62x10^-1 M HCN solution. NB the pKa forn HCN is 9.212.
4.90
9.21
0.58
11.32
13.42

Answer 1

For #1, this is a hydrolysis question.
NO2^- + HOH ==> HNO2 + OH^-

Kb = (Kw/Ka) = (HNO2)(OH^-)/(NO2^-)
Make an ICE chart and substitute into the Kb equation. I'm unsure of why you included the pKa for HCN. The pKa you want is HNO2.

For #2, ionize HCN.
HCN ==> H^+ + CN^-
Ka = (H^+)(CN^-)/(HCN)
Set up an ICE chart, substitute into the Ka expression above and solve for H^+, then convert to pH.

Post your work if you get stuck.