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Solutions

Assignment 4: The Solubility Product Constant, Ksp

Print out the assignment : Word | RTF | PDF
Show all work for your calculations. Be sure to highlight your final answer – circle it, underline it, whatever. Be sure to include the units for your answer. Failure to follow these directions may result in a loss of marks.
1.

Write the balanced equation and the solubility product constant expression, Ksp, for the each of the following dissociation reactions. All compounds are solids. One has been given as an example.

An important reminder – the seven diatomic molecules (H2, N2, O2, F2, Cl2, Br2, I2) ARE NOT diatomic as ions!

Reminders:

  • ion charges MUST BE included.
  • solids (and liquids) are NOT included in the equilibrium expression
  • don’t forget to include exponents when needed
  • polyatomic ions (e.g. CO32-) do not break apart
 
Compound
Equation
Ksp

(NH4)2S

(NH4)2S
equilibrium
2 NH4+(aq) + S2-(aq)

Ksp = [NH4+]2 [S2-]

CaS

 

 

K2SO4

 

 

Mg(OH)2

 

 

2. Consider the Ksp values for the following substances, all measured at 25 ° C
 

PbCrO4

2.0 × 10-16

PbSO4

1.3 × 10 -8

PbCO3

7.4 × 10-14
  A. Which substance is MOST soluble (dissolves the best) _____________________
B. Which substances is LEAST soluble (dissolves the worst) _____________________
3. Solutions are prepared by dissolving a sulfate salt (an ionic compound containing the sulfate ion) in water. Which one of the compounds listed below would we use in order to get the highest concentration of sulfate ion, SO42-?
  (a salt is an ionic compound that contains a positive ion other than hydrogen and a negative ion other than hydroxide).
 
A. CaSO4 Ksp = 2.6 × 10-4
B. SrSO4 Ksp = 7.6 × 10-7
C. BaSO4 Ksp = 1.5 × 10-9
D. RaSO4 Ksp = 4.0 × 10-11
4.

Calculate Ksp for a saturated nickel(II) sulfide, NiS , solution with a molar concentration of 3.27 × 10-11
  A. Begin with a balanced dissociation equation.
  B. From information provided in the question and the balanced equation, determine the concentration of the ions Ni2+ and S2-
  C. Write the Ksp expression for this reaction
  D. Substitute values into the equation and solve for the unknown (Ksp):
5. At 25 ° C, the concentration of Ce(OH)3 in a saturated solution is 5.1 × 10-6 M. Calculate Ksp
  A. Begin with a balanced equation:
  B. Determine the concentration of the ions in the solution. Be careful with [OH-].
  C. Write the Ksp expression, then substitute values into the equation and solve for the unknown, Ksp.
6.

Calculate the concentration of ions in a saturated solution of CaCO3 in water at 25 ° C.

Ksp for CaCO3 is 4.8 × 10-9.