Question

CHE 1102 Homework #8 – Due November 14                                                                                                                                                                                                   Name__________________________________

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Show work for full credit. Showing work means: 1) Write the equation you are using, 2) Fill in values (with units) in the equation, and 3) Show the final answer to correct sig figs/units. Intermediate math steps are not necessary.

1) What is the molar solubility of the following compounds based upon their given K_sp values:

a) Lithium chloride (K_sp = 388)                                                                                                         b) Sodium carbonate (K_sp = 33.4)

c) Calcium sulfate (K_sp = 2.19 x 10^‐4)                                                                                                                                                                            d) Magnesium phosphate (K_sp = 9.99 x 10^‐24)

2) What is the K_sp for the following compounds if the given masses can dissolve in 100. mL of water:

a) Potassium iodate (8.08 g / 100. mL)                                                                                                                                                                       b) Potassium iodide (144 g / 100. mL)

c) Barium fluoride (0.16 g / 100. mL)                                                                                                                                                                          d) Strontium acetate (41.1 g / 100. mL)

3) a) Sodium fluoride has a K_sp of 0.934. If 15.00 g of sodium fluoride is placed in a beaker containing 250. mL of water, what are the concentrations of the ions in solution after the solution is at equilibrium?

b) If solid in (a) was placed in 250. mL of a 0.200 M NaOH solution instead of pure water, what mass of sodium fluoride would dissolve?

4) 50.0 mL of 1.00 M sodium acetate and 50.0 mL of 1.00 M silver(I) nitrate are mixed together. What mass of silver(I) acetate precipitates from solution? K_sp for silver(I) acetate = 3.7 x 10^‐3

Answer 1

1.

a)

Ksp of LiCl = 388

Let the molar solubility of LiCl be s so,

LiCl(s) -> Li+(aq) + Cl-(aq)

s s

Ksp = [Li+][Cl-] = s*s = 388

so, s = sqrt(388) M

s = 19.7 M

b)

Ksp of Na2CO3 = 33.4

Let the molar solubility of Na2CO3 be s so,

Na2CO3(s) -> 2Na+(aq) + CO32-(aq)

2s s

Ksp = [Na+]²[CO32-] = (2s)²*s = 33.4

so, 4s³ = 33.4

s = (33.4/4)^1/3 M = 2.03 M

c)

Ksp of CaSO4 = 2.19*10^-4

Let the molar solubility of CaSO4 be s so,

CaSO4(s) -> Ca+2(aq) + SO42-(aq)

s s

Ksp = [Ca+2][SO42-] = s*s = 2.19*10^-4

so, s = sqrt(2.19*10^-4) M

s = 1.48*10^-2 M

d)

Ksp of Mg3(PO4)2 = 9.99*10^-24

Let the molar solubility of Mg3(PO4)2 be s so,

Mg3(PO4)2(s) -> 3Mg+2(aq) +2PO43-(aq)

3s 2s

Ksp = [Mg+2]³[PO43-]² = (3s)³*(2s)² = 9.99*10^-24

so, 108s⁵ = 9.99*10^-24

s = (9.99*10^-24/108)^1/5 M = 0.9845*10^-5 M