The pKa of ascorbic acid is 4.2. If I dissolve 1 gram of ascorbic acid in 1 liter of water at 25 degrees Celsius, what percentage of the ascorbic acid molecules will dissociate into C6H7O8- and H+ ions?
2007-07-02 11:12:29 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Ascorbic acid has pKa values of 4.2 and 11.6. At pH 4.2 it will be 50% dissociated.
2007-07-02 11:50:09 · answer #1 · answered by Uncle Al 5 · 0⤊ 0⤋
You need to master the material and do your homework. No one will take the test for you.
If the pKa = 4.2, the equilibruim constant =
10 ^-4.2 = [H+][A-] / [HA]
If x = [H+], it also = [A-] and [HA] = M-x where M = initial molarity of HA which you can calculate from the grams dissolved and the MW
Then 10^-4.2 = x^2/(M-x). You can approximate M-x~ M and then 10^4.2 = x^2/M
you should easily be able to take it from there.
2007-07-02 11:54:31 · answer #2 · answered by GTB 7 · 1⤊ 0⤋
Remember on how to find the ion dissociation using the formulas.... For an acid: H x conjugate base/ total acid concentration.
For a base: OH x conjugate acid(what the base looks like after it gains a H ion.)/all divided by the total base concentration.
2007-07-02 11:48:25 · answer #3 · answered by Anonymous · 0⤊ 0⤋