Respuesta :

Hagrid
Ka has the formula:

Ka = [H+] [X-] / [HX]

We have the following given:
[H+] = 4.15x10^-3
[HX] = 0.35

Since the acid dissociates in a ratio of 1 [H+] to 1 X,
[H+] = [X-]

Plugging in the values,
Ka = (4.15x10^-3)(4.15x10-3) / 0.35
Ka = 4.92x10^-5