Question

A phosphate buffer solution contain 0.08 M K2HPO4 and 0.12 M KH2PO4. pKa values for H3PO4 are 2, 6.8, and 12.2. Calculate the concentrations of

a) H3PO4
b) H2PO4-
c) HPO42-
d) H+
e) OH-
f) K+

Answer 1

You can get pH from HH equation. From that calculate pOH. I assume you can get K easily. Then for H3PO4 calculate the fraction in that from from H3PO4 = (H^+)^3/D where D is
(H^+)^3 + k1(H^+)^2 + k1k2(H^+) + k1k2k3