Ka Acid Dissociation Constant

Question 1

Assumption 1

Answer 1

Only a small amount of the weak acid dissociates so we can assume that

[HA(aq)]equilibrium = [HA(aq)]start

Ka= [H+][A-]
—————
[HA]start

Question 2

Ka expression

Answer 2

Ka= [H+][A-]
—————
[HA]start

Question 3

Assumption 2

Answer 3

The dissociation of acid is greater than the dissociation of water present in the solution. We can assume all the H+ ions come from the acid.

[H+] = [A-]

Question 4

Simplified Ka expression

Answer 4

Ka = [H+]^2
————
[HA]