Solubility Products

The solubility product

K_%7Bsp%7D

for calcium sulphate is given by:

K_%7Bsp%7D%20%3D%20%5B%5Ctext%7BCa%7D%5E%7B2%2B%7D%5D%20%5B%5Ctext%7BSO%7D_4%5E%7B2-%7D%5D.

Let the concentration of

%5Ctext%7BSO%7D_4%5E%7B2-%7D

at equilibrium be

x

. Since the dissociation of calcium sulphate produces one mole of

%5Ctext%7BCa%7D%5E%7B2%2B%7D

and one mole of

%5Ctext%7BSO%7D_4%5E%7B2-%7D

per mole of calcium sulphate, the concentration of

%5Ctext%7BCa%7D%5E%7B2%2B%7D

is also

x

. Thus, the solubility product becomes:

K_%7Bsp%7D%20%3D%20x%20%5Ccdot%20x%20%3D%20x%5E2%20%3D%202%20%5Ctimes%2010%5E%7B-5%7D.

Solving for

x

x%20%3D%20%5Csqrt%7B2%20%5Ctimes%2010%5E%7B-5%7D%7D%20%5Capprox%200.0045%20%5C%2C%20%5Ctext%7Bmol%2FL%7D.

Thus, the molar concentration of

%5Ctext%7BSO%7D_4%5E%7B2-%7D

at equilibrium is

0.0045%20%5C%2C%20%5Ctext%7Bmol%2FL%7D

Chapter Questions
1 MCQs