Solubility Product (Ksp)

Everything dissolves in water to a point.

Ksp expressions

CaF2 (s)

Ksp = [Ca 2+][F -]2

Ksp is really no different than any other K so far.

Ca 2+ (aq) + 2 F- (aq)

Calculating Ksp form solubility(M)

The solubility of Bi2S3 is 1.0 x 10 -15 M, calculate the Ksp for Bi2S3.

Write dissociation equation.Bi2S3 (s) I 1.0 x 10 -15 0 0C +(2)(1.0 x 10 -15) +(3)(1.0 x 10 -15)E 2.0 x 10 -15 3.0 x 10 -15

Ksp = [Bi3+]2[S2-]3

=1.1 x 10 -73

2 Bi 3+ (aq) + 3 S 2- (aq)

=(2.0 x 10 -15 )2(3.0 x 10 -15 )3

Calculating Solubility from Ksp

Calculate the solubility of copper (II) iodate from its Ksp value of 1.4 x 10 -7.

Cu(IO3)2 (aq) I M 0 0C +X +2XE X 2X

Ksp = [Cu2+][IO3-]2

4X3 = 1.4 x 10 -7

X = 3.3 x 10 -3 M Cu(IO3)2

Cu 2+ (aq) + 2 IO3 – (aq)

= (X)(2X)2 = 1.4 x 10 -7