Deck 16: Solubility and Precipitation Equilibria

Question 1

What is the molar solubility of AgCl at 25°C?

A) 8.0×10^-11
B) 1.6×10^-10
C) 1.3×10^-5
D) None of the above

Answer 1

C

Question 2

What is the molar solubility of PbI₂ at 25°C?

A) 1.5×10^-3
B) 6.0×10^-4
C) 3.0×10^-4
D) 1.0×10^-2
E) None of the above

Answer 2

A

Question 3

What is the solubility (in g/100cc) of PbI₂ at 25°C?

A) 10 mg
B) 28 mg
C) 50 mg
D) 69 mg
E) None of the above

Answer 3

D

Question 4

What is the solubility product expression for the dissociation of Fe(OH)₃?

A) [Fe³⁺][3OH^-]³
B) [Fe³⁺][OH^-]
C) [Fe³⁺][OH^-] / [Fe(OH)₃]
D) [Fe³⁺][3OH^-]³ / [Fe(OH)₃]
E) none of the above

Question 5

What is the maximum pH of a saturated Al(OH)₃ solution at 25°C?

A) 10.00
B) 10.51
C) 4.00
D) 3.5
E) None of the above

Question 6

Will Mg(OH)₂ be more or less soluble as the pH of a solution is raised?

A) More soluble
B) Less soluble
C) Changing the pH will have no effect on the solubility

Question 7

Will AgBr be more or less soluble as the pH of a solution is raised?

A) More soluble
B) Less soluble
C) Changing the pH will have no effect on the solubility

Question 8

Will PbSO₄ be more or less soluble as the pH of a solution is raised?

A) More soluble
B) Less soluble
C) Changing the pH will have no effect on the solubility

Question 9

What is the molar solubility of AgCl in 0.5 M NaCl at 25°C?

A) 3.2×10^-4
B) 1.3×10^-5
C) 3.2×10^-10
D) 5.0×10^-13

Question 10

What is the molar solubility of PbI₂ in 0.05 M KI at 25°C?

A) 1.5×10^-3
B) 2.8×10^-7
C) 5.6×10^-6
D) 3.8×10^-9

Question 11

A new stockroom worker wanted to prepare a 0.001 M CaSO₄ solution at 25°C. He massed out the correct stoichiometric amounts to make a 1.00 L stock solution. Once he diluted the massed CaSO4 with water, which of the following occurred.

A) [Ca²⁺] = [SO₄^2-] = 0.001 M
B) [Ca²⁺] = [SO₄^2-] < 0.001 M
C) a precipitate formed
D) a and c
E) b and c

Question 12

Calculate the pH at equilibrium in a solution that is initially 0.15 M Cu²⁺ and 0.50 M OH^-.

A) 13.00
B) 9.56
C) 11.56
D) 12.04
E) none of the above

Question 13

What is the molar solubility of Mn(OH)₂ in an aqueous solution buffered at pH=10 at 25°C?

A) 1.5×10^-5
B) 2.0×10^-5
C) 3.7×10^-5
D) 5.4×10^-8
E) none of the above

Question 14

How many grams of CuCl can be dissolved in 5.00 L of water before a precipitate forms?

A) 0.49 g
B) 0.11 g
C) 1.10 g
D) 0.22 g

Question 15

The solubility of AgBr increases with temperature. It is therefore

A) an exothermic process.
B) an endothermic process.
C) a spontaneous process.
D) a and c

Question 16

In general DS for a dissolution reaction is:

A) positive
B) negative
C) zero
D) Not enough data to answer the question.

Question 17

A researcher filled a 5.00 L flask with water and slowly added small amounts of CaC₂O₄. A small amount of precipitate was noticed after 0.0305 grams were added. What is the maximum value of K_sp for this compound?

A) 3.7×10^-5
B) 2.4×10^-4
C) 5.7×10^-8
D) 2.3×10^-9

Question 18

Exhibit 16-1
The following question(s) pertain to the sequence of events below:
Part A: A student prepares a saturated solution of Mg(OH)₂ by placing 200.0 grams of Mg(OH)₂ in a large beaker and adding 2 liters of water. There is a considerable amount of undissolved magnesium hydroxide in the bottom of the beaker. The student records the pH and then adds another liter of water to the beaker. There is still some solid in the bottom of the beaker.
Part B: The student then adds 500 ml of 0.5 M HCl to the beaker from Part A. He notices that there is slightly less precipitate in the bottom of the beaker.  
Part C: The student then adds 800 ml of 12 M HCl to the beaker from Part B. He notices that the precipitate dissolves.
Refer to Exhibit 16-1, Part A When he re-measures the pH he finds that

A) the pH went down.
B) the pH went up.
C) the pH is unchanged.
D) Not enough information to answer the question.

Question 19

Exhibit 16-1 The following question(s) pertain to the sequence of events below:
Part A: A student prepares a saturated solution of Mg(OH)₂ by placing 200.0 grams of Mg(OH)₂ in a large beaker and adding 2 liters of water. There is a considerable amount of undissolved magnesium hydroxide in the bottom of the beaker. The student records the pH and then adds another liter of water to the beaker. There is still some solid in the bottom of the beaker.
Part B: The student then adds 500 ml of 0.5 M HCl to the beaker from Part A. He notices that there is slightly less precipitate in the bottom of the beaker.  
Part C: The student then adds 800 ml of 12 M HCl to the beaker from Part B. He notices that the precipitate dissolves.
Refer to Exhibit 16-1, Part B. When he re-measures the pH he finds that

A) the pH went down.
B) the pH went up.
C) the pH is unchanged.
D) Not enough information to answer the question.

Question 20

Exhibit 16-1 The following question(s) pertain to the sequence of events below:
Part A: A student prepares a saturated solution of Mg(OH)₂ by placing 200.0 grams of Mg(OH)₂ in a large beaker and adding 2 liters of water. There is a considerable amount of undissolved magnesium hydroxide in the bottom of the beaker. The student records the pH and then adds another liter of water to the beaker. There is still some solid in the bottom of the beaker.
Part B: The student then adds 500 ml of 0.5 M HCl to the beaker from Part A. He notices that there is slightly less precipitate in the bottom of the beaker.  
Part C: The student then adds 800 ml of 12 M HCl to the beaker from Part B. He notices that the precipitate dissolves.
Refer to Exhibit 16-1, Part C. When he re-measures the pH he finds that

A) the pH went down.
B) the pH went up.
C) the pH is unchanged.
D) Not enough information to answer the question.

Question 21

Calculate the value of DG_rxn for the dissolution of AgCl at 95°C.

A) -53.3 kJ
B) 64.5 kJ
C) 53.3 kJ
D) 62.3 kJ
E) None of the above

Question 22

Calculate the value of K_sp for AgCl at 95°C.

A) 9.4×10^-1
B) 2.7×10^-8
C) 4.9×10^-30
D) 1.4×10^-9

Question 23

What is the molar solubility of AgCl at 95°C?

A) 1.6×10^-4
B) 9.7×10^-1
C) 2.2×10^-15
D) 3.7×10^-3

Question 24

Which carbonate, Ag₂CO₃, CaCO₃, or SrCO₃ is most soluble in water at 25°C?

A) Ag₂CO₃
B) CaCO₃
C) SrCO₃

Question 25

Which would have a higher pH at 25°C?

A) A saturated solution of Fe(OH)₃
B) A saturated solution of Fe(OH)₂
C) They would have the same pH
D) Concentration data is needed to answer the question

Question 26

Exhibit 16-2
The following question(s) pertain to calcium phosphate which has a molar solubility of 1.6×10^-7 at 25°C.
Refer to Exhibit 16-1. In the balanced chemical equation for the dissolution of calcium phosphate, the calcium ion has a stoichiometric coefficient of

A) 1
B) 2
C) 3
D) equal to that of the phosphate ion

Question 27

Exhibit 16-2
The following question(s) pertain to calcium phosphate which has a molar solubility of 1.6×10^-7 at 25°C.
Refer to Exhibit 16-1. Which of the following is the correct solubility product expression for the dissolution of calcium phosphate in water

A) [Ca²⁺][PO₄^3-]
B) [3Ca²⁺][2PO₄^3-]
C) [Ca²⁺]²[PO₄^3-]³
D) [2Ca²⁺]₂[3PO₄^3-]³
E) none of the above

Question 28

Exhibit 16-2
The following question(s) pertain to calcium phosphate which has a molar solubility of 1.6×10^-7 at 25°C.
Refer to Exhibit 16-1. What is the value of K_sp for calcium phosphate in water at 25°C?

A) 1.1×10^-32
B) 8.0×10^-31
C) 1.8×10^-39
D) 1.3×10^-38

Question 29

Exhibit 16-2
The following question(s) pertain to calcium phosphate which has a molar solubility of 1.6×10^-7 at 25°C.
Refer to Exhibit 16-1. In acidic solution the value of K_sp for calcium phosphate at °C will?

A) increase
B) decrease
C) stay the same

Question 30

Exhibit 16-2
The following question(s) pertain to calcium phosphate which has a molar solubility of 1.6×10^-7 at 25°C.
Refer to Exhibit 16-1. In acidic solution, the molar solubility of calcium phosphate at 25°C will

A) increase
B) decrease
C) stay the same

Question 31

What is the solubility of Al(OH)₃ in a buffer solution with a pH of 10.00 at 25°C? K_sp for Al(OH)₃ is 3.7 x 10^-15.

A) 6.6 mg^.L^-1
B) 8.4 mg^.L^-1
C) 19 mg^.L^-1
D) 290 mg^.L^-1
E) None of the above

Question 32

In general, DG, for dissolution reactions is _________ at low temperatures and _________ at high temperatures.

A) zero, negative
B) negative, positive
C) positive, negative
D) zero, positive
E) negative, zero

Question 33

The reason that solids do not factor into the K_sp law of mass action is because

A) the concentration of solids is infinite.
B) the activity is zero for the solid.
C) the activity is one for the solid.
D) A and B
E) None of the above