Question

1) At 25 °C, only 0.0670 mol of the generic salt AB is soluble in 1.00 L of water. What is the ?sp of the salt at 25 °C? AB(s)↽−−⇀A+(aq)+B−(aq)

2) A generic salt, AB3AB3, has a molar mass of 173173 g/mol and a solubility of 1.601.60 g/L at 25 °C.

What is the ?spKsp of this salt at 25 °C?

AB3(s)↽−−⇀A3+(aq)+3B−(aq)

3)The ?spKsp of manganese(II) hydroxide, Mn(OH)2, is 2.00×10−132.00×10−13. Calculate the solubility of this compound in grams per liter.

4) Above what Fe2+Fe2+ concentration will Fe(OH)2Fe(OH)2 precipitate from a buffer solution that has a pH of 8.098.09?

The ?spKsp of Fe(OH)2Fe(OH)2 is 4.87×10−17.

Answer 1

1)

At equilibrium:

AB <----> A+ + B-

   s s

Ksp = [A+][B-]

Ksp = (s)*(s)

Ksp = 1(s)^2

Ksp = 1(6.7*10^-2)^2

Ksp = 4.489*10^-3

Answer: 4.49*10^-3

2)

Molar mass of AB3= 173 g/mol

s = 1.6 g/L

To covert it to mol/L, divide it by molar mass

s = 1.6 g/L / 173 g/mol

s = 9.249*10^-3 mol/L

At equilibrium:

AB3 <----> A3+ + 3 B-

   s 3s

Ksp = [A3+][B-]^3

Ksp = (s)*(3s)^3

Ksp = 27(s)^4

Ksp = 27(9.249*10^-3)^4

Ksp = 1.975*10^-7

Answer: 1.97*10^-7

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