Question
Consider an amphoteric hydroxide, M(OH)2(s), where M is a generic metal.
M(OH)2 (s) <--> M^2+ (aq) + 2OH- (aq) Ksp=4e-16
M(OH)2 (s) + 2OH- (aq) <--> M(OH)4 ^2- (aq) Kf=0.06
Estimate the solubility of M(OH)2 in a solution buffered at pH= 7.0, 10.0, and 14.0
I'm not sure how to do this problem, please help
M(OH)2 (s) <--> M^2+ (aq) + 2OH- (aq) Ksp=4e-16
M(OH)2 (s) + 2OH- (aq) <--> M(OH)4 ^2- (aq) Kf=0.06
Estimate the solubility of M(OH)2 in a solution buffered at pH= 7.0, 10.0, and 14.0
I'm not sure how to do this problem, please help
Answers
DrBob222
.......M(OH)2(s) ==> M^2+ + 2OH^-
.......M(OH)2(s) + 2OH^- ==> M(OH)4^2-
Ksp = (M^2+)(OH^-)^2 = 4E-16
Kf = [M(OH)4^2-)/(OH^-)^2 = 0.06
Solubility = (M2+) + [M(OH)4^2-]
at pH 7, (H^+) = 1E-7 and OH^- = 1E-7
(Mg^2+) = Ksp/(1E-7)^2 = about 0.04 M
[Mg(OH)2^2-] = 0.06*(1E-7)^2 = 6E-16; therefore, clearly the complex ion is not the predominant factor at pH = 7. You can follow through at pH = 10 (pOH = 4) and pH 14 (pOH = 0).[Note: don't confused with pOH = 0, that is (OH^-) = 1.0M
These are ESTIMATES of the solubility.
.......M(OH)2(s) + 2OH^- ==> M(OH)4^2-
Ksp = (M^2+)(OH^-)^2 = 4E-16
Kf = [M(OH)4^2-)/(OH^-)^2 = 0.06
Solubility = (M2+) + [M(OH)4^2-]
at pH 7, (H^+) = 1E-7 and OH^- = 1E-7
(Mg^2+) = Ksp/(1E-7)^2 = about 0.04 M
[Mg(OH)2^2-] = 0.06*(1E-7)^2 = 6E-16; therefore, clearly the complex ion is not the predominant factor at pH = 7. You can follow through at pH = 10 (pOH = 4) and pH 14 (pOH = 0).[Note: don't confused with pOH = 0, that is (OH^-) = 1.0M
These are ESTIMATES of the solubility.
anon
thank you!
ConfusedStudent
^ this made no sense at all
Paula
I got the first two right but I cant figure out ph=14
what
^^ yeah how do you do it when the pH=14?
Person
For pH = 14.0 it'll be the same as your Ksp so 4e-16
Bobina
its not though. i put that and it was wrong...
yall are loserzz
wrong, sir. it is not the ksp...gosh how stupid.
Roxxie
For the pH of 14 the answer will be the Kf which is 0.06 for this problem
Marrtissey
Roxxie: you are a genius!!!!!
Kaitie
Roxxie: I know it's been 6 years and I've never met you, but I love you
Tito1347
You're correct Roxxie!!!! Genius!