Question

The next two questions refer to the following system: 3.5 x 10² mL of 3.2 M Pb(NO)₃ and2.0 x 10² mL of 0.020 M NaCl are added together.

1) Determine the ion product.

2) Will the precipitate occur?

Answer 1

concentration of Pb+2 = 3.5 x 10^2 x 3.2 / 350 + 200

                                   = 2.036 M

concentration of Cl- = 200 x 0.020 / 200 + 350

                                 = 7.27 x 10^-3 M

1)

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

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

    = (2.036) (7.27 x 10^-3 )^2

Q = 1.08 x 10^-4

ionic product = 1.08 x 10^-4

2)

Ksp of PbCl2 = 1.70×10^–5

Q = 1.08 x 10^-4

here Q > Ksp . so precipitate wil occur