Question

1.The molar solubility of iron(III) sulfide in a water solution is_________M

2.The equilibrium concentration of hydroxide ion in a saturated silver hydroxide solution is__________M

3.The equilibrium concentration of silver ion in a saturated silver chromate solution is___________M

4.A student measures the molar solubility of lead phosphate in a water solution to be 7.86×10^-10 M.
Based on her data, the solubility product constant for this compound is________

5.A student measures the molar solubility of barium phosphate in a water solution to be 6.48×10^-7 M.
Based on her data, the solubility product constant for this compound is________

6.The solubility of Mg(OH)₂ is measured and found to be 9.29×10^-3 g/L. Use this information to calculate a K_sp value for magnesium hydroxide. Ksp=________?

7.The solubility of Ag₂S is measured and found to be 7.12×10^-15 g/L. Use this information to calculate a K_sp value for silver sulfide. Ksp=________?

8.The solubility of ZnCO₃ is measured and found to be 5.04×10^-4 g/L. Use this information to calculate a K_sp value for zinc carbonate.   Ksp=________?

Answer 1

1)

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

the solubility product constant is given by

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

now

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

let 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 is 1.0533 x 10-18 mol / L

2)

AgOH ----> Ag+ + OH-

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

now

AgOH ---> Ag+ + OH-

let 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 is 1.414 x 10-4 M

3)

Ag2Cr04 ----> 2 Ag+ + Cr042-

Ksp = [Ag+]^2 [Cr042-] = 1.12 x 10-12

now

Ag2Cr04 ----> 2 Ag+ + Cr042-

let the molar solubility of Ag2Cr04 be s

then at equilibrium

[Ag+] = 2s

[Cr042-] = s

so

Ksp = [Ag+]^2 [Cr042-]

Ksp = [2s]^2 [s]

Ksp = 4s3

4s3 = 1.12 x 10-12

s =6.542 x 10-5

now

[Ag+] = 2s

[Ag+] = 2 x 6.542 x 10-5

[Ag+] = 1.3084 x 10-4

so

the equilibrium concentration of Ag+ ion is 1.3084 x 10-4 M

4)

Pb3(PO4)2 ---> 3 Pb+2 + 2 P043-

let the molar solubility be s

then

[Pb+2] = 3s

[P043-] = 2s

now

Ksp = [Pb+2]^3 [P043-]^2

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

Ksp = 108s^5

given

molar solubility (s) = 7.86 x 10-10

so

Ksp = 108 x (7.86 x 10-10)^5

Ksp = 3.118 x 10-44

so

the value of solubility product constant is 3.118 x 10-44

5)

Ba3(PO4)2 ---> 3 Ba+2 + 2 P043-

let the molar solubility be s

then

[Ba+2] = 3s

[P043-] = 2s

now

Ksp = [Ba+2]^3 [P043-]^2

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

Ksp = 108s^5

given

molar solubility (s) = 6.48 x 10-7

so

Ksp = 108 x (6.48 x 10-7)^5

Ksp = 1.234 x 10-29

so

the value of solubility product constant is 1.234 x 10-29

6)

we know that

molar solubility = solubility in g/L / molar mass

so

molar solubility of Mg(OH)2 = 9.29 x 10-3 / 58.3197

molar solubility of Mg(OH)2 = 1.593 x 10-4 M

now

Mg(OH)2 ----> Mg+2 + 2 OH-

let the molar solubility of Mg(OH)2 be s

then

[Mg+2] = s

[OH-] = 2s

now

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

Ksp = [s] [2s]^2

Ksp = 4s3

Ksp = 4 x ( 1.593 x 10-4)^3

Ksp = 1.617 x 10-11

so

the Ksp value of magnesium hydroxide is 1.617 x 10-11

7)

we know that

molar solubility = solubility in g/L / molar mass

so

molar solubility of Ag2S = 7.12 x 10-15 / 247.8

molar solubility of Ag2S = 2.8733 x 10-17 M

now

Ag2S ----> 2 Ag+ + S-2

let the molar solubility of Ag2S be s

then

[Ag+] = 2s

[S-2] = s

now

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

Ksp = [2s]^2 [s]

Ksp = 4s3

Ksp = 4 x ( 2.8733 x 10-17)^3

Ksp = 9.49 x 10-50

so

the Ksp value of silver sulfide is 9.49 x 10-50

8)

molar solubility = solubility in g/L / molar mass

so

molar solubility of ZnC03 = 5.04 x 10-4 / 125.39

molar solubility of ZnC03 - 4.02 x 10-6 M

now

ZnC03 ---> Zn+2 + C032-

let the molar solubility be s

then

[Zn+2] = s

[C032-] = s

now

Ksp = [Zn+2] [C032-]

Ksp = [s] [s]

Ksp = s2

Ksp = ( 4.02 x 10-6)^2

Ksp = 1.6156 x 10-11

so

the value of Ksp for zinc carbonate is 1.6156 x 10-11