Answer to Question #119976 in General Chemistry for Cass

Question

5. Someone else hears that pop is acidic, but they don’t pay attention to the acid involved. They have heard that Phosphoric acid (Ka = 7.5 *10 -3) has some food grade application, so they decide to use it. Again they dissolve 5.0 grams/1.0L. What is the pH of this solution? (Note: for this problem it is still ok to simplify the quadratic, If you want you could actually solve it in the true form though).

Answer 1

Cm=5/98= 0.051 M.

X=√0.051 x 7.5 x 10-3.

X= 0.02.

pH=- lg[0.02] = 1.68.