Question

For aluminum hydroxide, Al(OH)₃ the K_sp = 1 x 10^-33 . Use this fact to show why aluminum does not react with aqueous acetic acid.

Answer 1

Solution :-

Al(OH)3 ------ > Al^3+ + 3OH-

                          x            3x

ksp = [x][[3x]^3

ksp = 4x^27

1.33*10^-33 = 27x^4

1.33*10^-33 / 27 = x^4

4.93*10^-35 = x^4

taking 4th root of both sides we get

2.65*10^-9 = x

so the concnetration of the OH-= 3*2.65*10^-9 = 7.95*10^-9 M

this is very low concentration of the OH-

so Al(OH)3 dissociation very very small therfore it does not react with acetic acid.