If given the Ka or Kb and pKa and pKb, how do you find the initial concentration of a weak acid/base in a solution given the pH? Is there an equation for this? I can't find anything in my notes and am not sure what to look for.

Answer 1

HA ==> H^+ + A^-

Ka = (H^+)(A^-)/(HA)

Given the pH, convert to (H^+). That is the same as (A^-). You are given either Ka or pKa. That leaves only one unknown, (HA).