Solubility Product Practice Problems

Solubility Practice Questions

Note:Ksp Values can be obtained from any online resources or your text book.

Trial Ksp is also sometimes referred to as Qsp

Conditions for precipitation are Qsp > Ksp.

If Qsp = Ksp the system is in equilibrium

If Qso < Ksp there will be no precipitation taking place if the two solutions are mixed.

Practice Questions:

1. One liter of water is able to dissolve 2.15 x 10-3 mol of PbF2. What is the Ksp for PbF2?

2. The molar solubility of CoCO3 in a 0.10 M Na2CO3 solution is 1.0 x 10-9 mol/L. What is Ksp for CoCO3?

3. The molar solubility of PbF2 in a 0.10 M Pb(NO3)2 solution is 3.1 x 10-4 mol/L. Calculate Ksp for PbF2.

4. What is the molar solubility of AgBr in water?

5. What is the molar solubility of Ag2CO3 in water?

6. What is the molar solubility of AgI in 0.20 M NaI solution?

7. What is the molar solubility of Fe(OH)3 in a solution with a hydroxide ion concentration of 0.050 M?

8. Will a precipitate of CaSO4 form in a solution if the Ca2+ concentration is 0.0025 M and the SO4 concentration is 0.030 M? For CaSO4, Ksp = 2.4 x 10-5.

9. Will a precipitate form in a solution containing 3.4 x 10-4 M CrO4-2 and 4.8 x 10-5 M Ag+?

10. Will a precipitate of PbSO4 form if 100 mL of 1.0 x 10-3 M Pb(NO3)2 solution is added to 100 mL of 2.0 x 10-3 M MgSO4 solution?

11. Will a precipitate of PbCl2 form if 50.0 mL of 0.10 M Pb(NO3)2 solution is added to 20.0 mL of 0.040 M NaCl solution?

12. Barium Sulfate is so insoluble that it can be swallowed without significant danger, even though Ba2+ is toxic. At 25oC, 1.00L of water dissolves only 0.00245 g of BaSO4. What is the Ksp of Barium Sulfate?

13. A student prepared a saturated solution of CaCrO4 and found that when 100 mL of this solution was evaporated, 0.416 g of CaCrO4 was left behind. What is the value of Ksp for this type?

14. Copper (I) Chloride has Ksp = 1.9 x 10-7. Calculate the molar solubility of CuCl in

a) pure water

b) 0.020 M HCl

c) 0.020 M MgCl20.020 M Au(NO3)3

15. At 25oC the value of Ksp for LiF is 1.7 x 10-3 and for BaF2, 1.7 x 10-6. In terms of moles per liter, which salt is the more soluble in water? Calculate the solubility of each in these units.

16. Chalk is CaCO3 and at 25oC it’s Ksp = 4.5 x 10-9. How many grams of CaCO3 dissolve in 100 mL of water?

17. What is the molar solubility of Mg(OH)2 in 0.10 M NaOH. Ksp of MgCl2is 7.1 x 10-12.

18. Does a precipitate of PbCl2 form when 0.0100 mol of Pb(NO3)2 and 0.0100 mol of NaCl are dissolved in 1.00L of solution.

19. Silver acetate, AgCH3COO, had Ksp = 4 x 10-3. Does a precipitate form when 0.010 mol of AgNO3and 0.30 mol of Ca(CH3COO)2 are dissolved in a total volume of 1.00 L of solution.

20. Does a precipitate of PbBr2 form if 50.0 mL of 0.010 M Pb(NO3)2 is mixed with

a) 50.00 mL of 0.010 M KBr?

b) 50.0 mL of 0.10 M NaBr?

21. Would a precipitate of silver acetate form if 18.0 mL of 0.10 M AgNO3 were added to 40.0 mL of 0.024 M NaC2H3O2, Ksp = 4 x 10-3.

22. Suppose that 50.0 mL of 0.10 M AgNO3 were added to 50.0 mL of 0.050 M NaCl solution

a) What weight of AgCl would be formed?

b) What would be the final concentrations of all the ions contributed by these salts?

23. Drinking water often contains dissolved chloride and/or calcium ions. Devise a procedure to test which of these ions is present in a sample of tap water.

24. A solution contains a least 0.8 mol/L of each of the following ions: Ag+, Ba2+, Mg2+. Use a flow chart to illustrate a procedure that could be used to separate these ions from each other.

25. A solution contains a least 0.8 mol/L of each of the following ions: Pb2+, Ag+, Mg2+, Fe2+. Use a flow chart to illustrate a procedure that could be used to separate these ions from each other.

26. For the following equations, write the final balanced equation with the proper precipitates and ions.

a) MgS + Zn(NO3)2 =>

b) Pb(ClO3)2 + KI =>

c) Ca(OH)2 + FeSO4 =>

d) Li2CO3 + AgCH3COO =>

Solubility Practice Questions: Solution

1.

PbF2 <=>Pb2+ + 2F C = n/v

2.15×10-3 2.15×10-3 4.3×10-3 C = 2.15×10-3 mol

1L

Ksp = [Pb2+][F]2 C = 2.15×10-3 mol/L

Ksp = (2.15×10-3)(4.3×10-3)2

Ksp = 3.98×10-8

2.

CoCo3 <=>Co2+ + CO32-                     Na2CO3 =>2Na+ + CO3

1×10-9 1×10-9 1×10-9 0.1 0.2 0.1

Ksp = [Co2+][Co32-]

Ksp = (1×10-9)(1×10-9 + 0.1)

Ksp = 1×10-10

3.

PbF2 <=>Pb2+ + 2F                     Pb(NO3) =>Pb2+ + 2NO3

3.1×10-4 3.1×10-4 6.2×10-4 0.1 0.1 0.2

Ksp = [Pb2+][F]2

Ksp = (3.1×10-4 + 0.10)(6.2×10-4)2

Ksp = 3.86×10-8

4.

Ksp = 5.0×10-13 AgBr Ag+ + Br

x x x

Ksp = [Ag+][Br ]

5.0×10-13 = x2

x = 7.07×10-7

∴ Molar solubility = 7.07×10-7

5.

Ag2CO3 <=>2Ag+ + CO3 Ksp = 8.1×10-12

2x x

Ksp = [Ag+]2 [CO3 ]

8.1×10-12 = 4x3

x3 = 2.015×10-12

x = 1.3×10-4

∴ Molar solubility is 1.3×10-4


6.

AgI <=>Ag+ + I                                      NaI=> Na+ +   I

  x              x          x                                                       0.2   0.2

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Ksp = [Ag+][ I ]

8.3×10-17 = (x)(x + 0.2) Negligible because Ksp is very small.

x = 4.15×10-16

∴ Molar solubility is 4.15×10-16

7.

Fe(OH)3 <=>Fe3+ + 3OH                OH = 0.05

x x 3x

Ksp = [Fe3+][ OH ]3

1.6×10-39 = (x)(3x + 0.05)3 Negligible because Ksp is so small

Since the value of Ksp is very small the value of x will be negligible hence can be ignored

x = 1.28×10-35

∴ Molar solubility is 1.28×10-35

8.

Trial Ksp = [Ca][SO4 ]

Trial Ksp = (0.0025)(0.03)

Trial Ksp = 7.5×10-5 Ksp = 2.4×10-5

∵ Trial Qsp > Ksp

∴ Precipitate will form

9.

Ksp = [Ag+]2 [CrO4 -2 ] Ag2CrO4 =>2Ag+ + CrO42-

Trial Ksp = (4.8×10-5 )2 (3.4×10-4 )

Trial Ksp = 7.83×10-13

∵ Trial Qsp < Ksp

∴ No precipitate will form

10.

Pb(NO3)2 Pb+2 + 2NO3MgSO4 =>Mg2+ + So4 2 –

C1V1 = C2V2 C1V1 = C2V2

(1.0×10-3 )(100) = C2 (200) (2.0×10-3 )(100) = C2 (200)

C2 = 5.0×10-4 C2 = 1×10-3

PbSO4 => Pb+ + SO42-

Trial Qsp = [Pb2+][SO42 – ] Ksp = 6.3×10-7

Trial Qsp = (5.0×10-4)(1×10-3)

Trial Qsp = 5×10-7

∵ Trial Qsp < Ksp

∴ No precipitate will form