Question

1) The molar solubility of PbI2 is 1.5X10-3 mol/L. PbI2(s) ? Pb2+(aq) + 2I-(aq) What is the molar concentration of iodide ion in a saturated PbI2 solution in mol/L? Hint: Consider mol ratios. Don't use scientific notation. Use 2 significant figures. ________

2) The molar solubility of PbI2 is 1.5X10-3 mol/L. PbI2(s) ?Pb2+(aq) + 2I-(aq) Determine the solubility constant, ksp, for lead(II) iodide: ksp = [Pb2+][I-]2 Don't use scientific notation. Use 2 significant figures. ________

3) How is the molar solubility affected by addition of lead(II) nitrate to the solution? Molar solubility = moles of salt that dissolve per L of solution. Hint: Consider Le Chatelier’s Principle, you are adding Pb2+ ions. PbI2(s)?Pb2+(aq) + 2I-(aq)

A) Increases molar solubility, equilibrium is shifted to the right. B) Decreases molar solubility, equilibrium is shifted to the left. C) No change, equilibrium can never be altered!

4) The molar solubility of PbI2 is 1.5X10-3 mol/L. PbI2(s) ?Pb2+(aq) + 2I-(aq) Determine the solubility constant, ksp, for lead(II) iodide: ksp = [Pb2+][I-]2 Don't use scientific notation. Use 2 significant figures. ________

Answer 1

1)

PbI2(s) ⇌ Pb2+(aq) + 2I-(aq)

           s          s

Ksp = [Pb2+] [2I-]

1.5*10^-3 = s*s

s^2 = 1.5*10^-3

s = 0.039 M

Answer: 0.039 M

2)

PbI2(s) ⇌ Pb2+(aq) + 2I-(aq)

           s          s

Ksp = [Pb2+] [2I-]

Ksp = s*s

Ksp = s^2

Ksp = (1.5*10^-3)^2

Ksp = 2.3*10^-6

Ksp = 0.0000023

Answer: 0.0000023

3)

when we add Pb(NO3)2 in PbI2 equilibrium, we are adding a common ion Pb2+

PbI2(s) ⇌ Pb2+(aq) + 2I-(aq)

Adding Pb2+, is like adding a product.

So, according to LeChatellier’s principle the equilibrium will shift to reactant side

So, solubility will decrease for PbI2

Answer: B) Decreases molar solubility, equilibrium is shifted to the left.

4)

This question is same as question number 2

PbI2(s) ⇌ Pb2+(aq) + 2I-(aq)

           s          s

Ksp = [Pb2+] [2I-]

Ksp = s*s

Ksp = s^2

Ksp = (1.5*10^-3)^2

Ksp = 2.3*10^-6

Ksp = 0.0000023

Answer: 0.0000023

Answer 2