CADMIUM SOLUBILITY AND pH Cadmium is a toxic metal. It can be removed from water by chemical precipitation of solid cadmium hydroxide, Cd(OH), The drinking water standard for cadmium is 5 μg L (0.005 mg L). The solubility product of Cd(OH), is 2 x 10" M. What is the minimum pH necessary to reduce the dissolved cadmium ion concentration to the standard?

Explanation:

It is known that,

      Molar mass of Cd = 112.41 g/mol

Standard concentration of Cd = 0.005 mg/L = g/L

Hence, we will calculate the molarity as follows.

        Molarity =

                       = M

Equation for the reaction is as follows.

          M

Also,

                      =

                      =

Relation between pH and concentration of hydrogen ions is as follows.

               pH =

                     =

                     = 10.82

Thus, we can conclude that a minimum pH of 10.82 is necessary to reduce the dissolved cadmium ion concentration to the standard.