Question

What is the ratio of the molarities of po3− 4 and hpo2− 4 ions in a buffer solution having a ph of 10.92?

Answer 1

when we have Pka = 12.68 (missing in your question)

so by using H- H equation we can get the molarity ratio:

PH = Pka + ㏒ [conjugate base/ weak acid]

when we have PH= 10.92

and Pka = 12.68

so by substitution:

10.92 = 12.68 + ㏒ [PO3-4]/[HPO2-4 ]

∴ [PO3-4]/[HPO2 -4] = 0.017