Posted by GWM on .
2.Glycolic acid is often used in “facial peels” and has a Ka of 1.5x10^-4. If a movie star is to have a solution of pH 2.1 applied to her face at night, what concentration of glycolic acid solution should be made up (assuming that it is a monoprotic acid, and that it dissolves freely in water)
HG ==> H^+ + G^-
Ka = (H^+)(G^-)/)HG) = 1.5 x 10^-4
Convert pH 2.1 to (H^+), substitute into Ka expression for (H^+) and (G^-) and solve for (HG). That will give you concn HG in moles/L.
By the way, Juan, Robert, Samantha, Cindy, GWM, etc etc, we really appreciate it if you keep the same screen name in a series of postings. It helps us keep everyone straight and aids is us answering repetitive type questions to help you the most. Not only are you asking the same kind of question, but you are using the same style, the same numbering system, AND the same computer. I know some students think we don't like to answer too many questions by the same student; however, that is not true. We welcome all questions but it helps us if we KNOW the questions are from the same person.