Chemistry

Problem

Which of the following expressions corresponds to the equilibrium constant

K_a

for the dissociation of a generic weak acid

HX

in water (

HX + H_2O

ightleftharpoons

H_3O^+ + X^-

)? a)

K_a = \dfrac{[HX]}{[H_3O^+][X^-]}

K_a = \dfrac{[H_3O^+][X^-]}{[HX][H_2O]}

K_a = \dfrac{[H_3O^+][X^-]}{[HX]}

K_a = \dfrac{[X^-]}{[HX]}