Lactic acid has a pK_a of 3.08. What is the approximate degree of dissociation of a 0.35 M solution of lactic acid?

Question

Quizplus · Accepted Answer

Using the equation for percent dissociation of a weak acid: percent dissociation = (Ka / [HA]) x 100%, we can plug in the given pKa value (taking the negative log gives us the Ka value) and the concentration of lactic acid to get: percent dissociation = (10^-pKa / [HA]) x 100% = (10^-3.08 / 0.35) x 100% = 4.8%. Therefore, the best choice is C, with an approximate degree of dissociation of 4.8%.

Lactic Acid Has a PKa of 3

Lactic Acid Has a PK_a of 3