Calculate the pH of the solute in an aqueous solution of 0.0047 M codeine, if the pKa of itsconjugate acid is 8.21.

Question

What is the percentage protonation of the solute?

Answer 1

If we all codeine, C, then the hydrolysis is
C + HOH ==> HC^+ + OH^-
Kb = (Kw/Ka) = (OH^-)^2/(C)
Substitute into the Kb expression and solve for OH^-, convert to pOH, then to pH.