Question

1. After mixing an excess PbClh with a fixed amount of water, it is found that the equilibrium concentration of Pb2'sL6x10 a) (5 points)Write the dissolution reaction and the associate equilibrium expression (Kup b) (10 points) Calculate the value of Kap for PbCl. c) (10 points) How many moles of PbClh will dissolve in 1.0L of 0.51 M NaCI solution?

Answer 1

1)

a)

dissolution equation :

PbCl2 (s)   ------------->   Pb+2 (aq) +   2 Cl- (aq)

Ksp expression :

Ksp = [Pb+2] [Cl-]^2

b)

concentration of Pb+2 = 1.6 x 10^-2 M

concentration of Cl- = 0.032 M

Ksp = [Pb+2] [Cl-]^2

     = 1.6 x 10^-2 x (0.032)^2

Ksp = 1.64 x 10^-5

c)

PbCl2 (s)   ------------->   Pb+2 (aq) +   2 Cl- (aq)

                                          S                  0.51

Ksp = [S] (0.51)^2

1.64 x 10^-5 = S x (0.51)^2

S = 6.30 x 10^-5

moles of PbCl2 dissolve = 6.30 x 10^-5 mol