Question

DETERMINE THE SOLUBILITY PRODUCT CONSTANT (and can you recommend a good Ksp table? Thanks very much!):

a) A student measures the molar solubility of iron(III) hydroxide in a water solution to be 2.17×10^-10 M.
Based on her data, the solubility product constant for this compound is ___________

b) A student measures the SO₄^2- concentration in a saturated aqueous solution of silver sulfate to be 1.66×10^-2 M.
Based on her data, the solubility product constant for silver sulfate is ____________

c) A student measures the molar solubility of lead fluoride in a water solution to be 2.13×10^-3 M.
Based on her data, the solubility product constant for this compound is ___________

Answer 1

a) Fe(OH)₂ ----> Fe²⁺ + 2 OH^-

the solubility product constant is given by Ksp = [Fe²⁺] [OH^-]²

let the molar solubility be s then [Fe²⁺] = s [OH^-] = 2s

now Ksp = [Fe²⁺] [OH^-]²

Ksp = [s]*[2s]²

Ksp = 4*s³ = 4 *(2.17*10^-10M)² = 4.087*10^-29 M³

Based on her data, the solubility product constant for this compound is 4.087*10^-29 M³

b) Ag₂(SO)₄ ----> 2Ag⁺ + SO₄^2-

the solubility product constant is given by Ksp = [Ag²⁺]² [SO₄^2-]

let the molar solubility be s then [Ag²⁺] = 2s [SO₄^2-] = s

[Ag²⁺] = [SO₄^2-]

now Ksp = [Ag²⁺]² [SO₄^2-]

Ksp = [2s]²*[s]

Ksp = 4*s³ = 4 *(1.66*10^-2M)³ = 1.829*10^-5 M³

Based on her data, the solubility product constant for this compound is 1.829*10^-5 M³

c) PbF₂ ----> Pb²⁺ + 2 F^-

the solubility product constant is given by Ksp = [Pb²⁺] [F^-]²

let the molar solubility be s then [Pb²⁺] = s [F^-] = 2s

now Ksp = [Pb²⁺][F^-]²

Ksp = [s]*[2s]²

Ksp = 4*s³ = 4 *(2.13*10^-3M)³ = 3.865*10^-8 M³

Based on her data, the solubility product constant for this compound is 3.865*10^-8 M³