Chapter 25, Problem 25.3P

Interpretation Introduction

Interpretation:

The percentage of the un-ionized form, mono-anion form, and the di-anion form for methyl phosphate at pH 7.4 are to be determined.

Concept introduction:

There are two protons in methyl phosphate which can dissociate. So, there are three forms which are un-ionized form (charge = 0), mono-ionized form (charge = -1) and di-ionized form (charge = -2).

If the value of $\mathrm{p}\mathrm{H}$ is more than $\mathrm{p}{\mathrm{K}}_{\mathrm{a}}$, this indicates that the acid is about $99\%$ dissociated.

If the value of $\mathrm{p}\mathrm{H}$ is one unit higher than that of $\mathrm{p}{\mathrm{K}}_{\mathrm{a}}$, this indicates that the acid is about $90\%$