posted by Valerie .
What is the pH of a 0.50 M solution of NaNO2 if the Ka of H20x = 4.5 x 10^-4. I know that you use the Ka to find Kb and solve from there, but why?
NO2^- is a base; it attracts a H^+ from water and Kb is the strength as a base.
So you're saying that if you have the Ka of any acid and you can use the ionization constant of water to find Kb of its conjugate base?
I didn't say that in so many words but, yes, you can do that. Why? Because
KaKb = Kw.
If you know EITHER Ka or Kb you can calculate the other one from this relationship and Kw.