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Titration: Calculating concentration of weak acid, Ka, PKa?
In the titration of 10mL of an unknown weak acid (HX) with a strong base that has a molarity of 0.1002 M, the equivalence volume was found to be 19.20 mL.
a) Calculate the concentration of HX
b) If the initial pH of the solution was recorded as 3.12, what is the Ka and pKa of HX.
Please explain how to arrive at answers. I don't need the answers so much as I need to know how to do it.
1 Answer
- TheOnlyBeldinLv 71 decade agoFavorite Answer
a) MaVa = MbVb
Solve for Ma (Mb = 0.1002, Vb = 19.20, Va = 10)
b)Once you have Ma:
convert pH to [H+] ---> [H+] = 10^-pH (should be 7.59 x 10^-4)
Ka = [H+][X-] / [HX] = (7.59 x 10^-4)^2 / (Ma - 7.59 x 10^-4) (there is no other source of X-, so it must come from the dissociation of HX, thus [X-] = [H+])
pKa = -log Ka
