Question

1. For cerium (III) hydroxide, Ce(OH)3, Ksp equals 2.0x10 –20. Calculate the molar solubility. What is the value of ÆGo for the dissolution of cerium hydroxide?

b. What is the molar solubility of Mg(OH)2 in a solution containing 1.0 x 10 –1 M NaOH? Ksp of Mg(OH)2 is 1.8 x 10 –11

c. The Ksp for AgCl at 25.0oC is 1.782x10–10. The Ksp at 35.0oC Is 4.159x10–10. What are ÆHo and ÆSo for the dissolution reaction of AgCl(s).

d. Ka for acetic acid is1.754x10-5 at 25oC. At 50.0oC,Kais1.633x10–5. What are ÆHo and ÆSo for the ionization of acetic acid?

Answer 1

1. For cerium (III) hydroxide, Ce(OH)3, Ksp equals 2.0x10 –20. Calculate the molar solubility. What is the value of ÆGo for the dissolution of cerium hydroxide?

Ce(OH)3 ---------------> Ce+3   + 3 OH-

                                        S             3S

Ksp = S x (3S)^3

2.0 x 10^-20 = 27 S^4

S = 5.2 x 10^-6 M

molar solubility = 5.2 x 10^-6 M

delta Go = - RTlnKsp

               = - 8.314 x 10^-3 x 298 x ln (2 x 10^-20)

delta Go = 112.4 kJ/mol

b. )

Mg(OH)2   --------------> Mg+2 + 2 OH-

                                       S            0.1

Ksp = [Mg+2][OH-]^2

1.8 x 10^-11 = S x (0.1)^2

S = 1.8 x 10^-9 M

molar solubility = 1.8 x 10^-9 M