Question

If HA, an acid, is 15 percent dissociated in a 2.00 molar solution, what is the Ka for the solution? A. 5.3 × 10-2 B. 6.4 × 10-3 C. 1.1 × 10-2 D. 1.2 × 10-2

Answer 1

Answer: 0.3

Explanation:

We know that

Ka = [H+] * [A-] / [HA]

And the acid is 15 % dissociated means that

[A-] / [HA] *100 = 15%

So

[A-] / [HA] = 0.15

Then we know that [H+] = [A-] = 2 molar

Replacing we have

Ka = 2 molar * 0.15 = 0.3