The volume of NaOH added halfway to the equivalence point represents the pH when the acid is "half-neutralized". At this point, the [HA] = [A-]. If the equation for this
neutralization reaction is: HA + H₂0 > H₃0+ + A-, then the equilibrium constant expression would be:
Ka = [H₃O+] [A-] / [HA]
Since [HA] = [A-], then these values would cancel in the equation above and Ka = [H₃0+].
(a) Determine the [H₃O+] of the KHP solution using the average moles of acid used and the volume of water added.
(b) What is the Ka of this solution?
