Question

A.) The molar solubility of iron(III) sulfide in a water solution is  M.

B.)The equilibrium concentration of hydroxide ion in a saturated silver hydroxide solution is  M.

Answer 1

1) The equation is

Fe2S3 -----> 2 Fe+3 + 3 S-2

Now from the equation the solubility product constant is:

Ksp = [Fe+3]^2 [S-2]^3

So

Fe2S3 ---> 2 Fe+3 + 3 S-2

let us assume the molar solubility be s

then

[Fe+3] = 2s

[S-2] = 3s

now

Ksp = [Fe+3]^2 [S-2]^3

Ksp = [2s]^2 [3s]^3

Ksp = 108 s^5

we know that

Ksp value of Fe2S3 is 1.4 x 10-88

so

1.4 x 10-88 = 108 x s^5

s = 1.0533 x 10-18

so

the molar solubility of iron (III) sulfide = 1.0533 x 10-18 mol / L

2)
The equation is
AgOH ----> Ag+ + OH-
From the equation

Ksp = [Ag+] [OH-] = 2 x 10-8

now

AgOH ---> Ag+ + OH-

let us assume the molar solubility of AgOH be s

then at equilibrium

[Ag+] = s

[OH-] = s

now

Ksp = [Ag+] [OH-]

Ksp = [s] [s]

Ksp = s2

s2 = 2 x 10-8

s = 1.414 x 10-4

so

the equilibrium concentration of Hydroxide ion = 1.414 x 10-4 M