Question

a) The molar solubility of barium carbonate in a 0.249 M potassium carbonate solution is _________M.

b) The solubility of Co(OH)₂ is measured and found to be 3.61×10^-4 g/L. Use this information to calculate a K_sp value for cobalt(II) hydroxide.

K_sp = ______

c) The solubility of Ag₂SO₄ is measured and found to be 5.17 g/L. Use this information to calculate a K_sp value for silver sulfate.

K_sp =_________

Answer 1

a)

K2CO3 here is Strong electrolyte

It will dissociate completely to give [CO32-] = 0.249 M

At equilibrium:

BaCO3 <----> Ba2+ + CO32-

   s 0.249 + s

Ksp = [Ba2+][CO32-]

2.58*10^-9=(s)*(0.249+ s)

Since Ksp is small, s can be ignored as compared to 0.249

Above expression thus becomes:

2.58*10^-9=(s)*(0.249)

2.58*10^-9= 1(s)^1 * 0.249

s = 1.04*10^-8 M

Answer: 1.04*10^-8 M

b)

Co(OH)2 ----> Co2+ + 2 OH-

   s 2s

Molar mass of Co(OH)2= 92.95 g/mol

s = 3.61*10^-4 g/L

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

s = 3.61*10^-4 g/L / 92.95 g/mol

s = 3.884*10^-6 g/mol

At equilibrium:

Ksp = [Co2+][OH-]^2

Ksp = (s)*(2s)^2

Ksp = 4(s)^3

Ksp = 4(3.884*10^-6)^3

Ksp = 2.34*10^-16

Answer:2.34*10^-16

c)

Ag2SO4 ----> 2 Ag+ + SO42-

   2s s

Molar mass of Ag2SO4= 311.87 g/mol

s = 5.17 g/L

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

s = 5.17 g/L / 311.87 g/mol

s = 1.658*10^-2 g/mol

At equilibrium:

Ksp = [Ag+]^2[SO42-]

Ksp = (2s)^2*(s)

Ksp = 4(s)^3

Ksp = 4(1.658*10^-2)^3

Ksp = 1.82*10^-5

Answer: 1.82*10^-5