Question

Calculate molar solubility of ZnCO₃ in a buffer solution of pH = 7

Answer 1

To consider the molar solubility following reactions are taken into account

                                 …… (1)

                     …… (2)

                        …… (3)

Add equations (1) and (2) to obtain the equation (3) and subsequently multiply the dissociation constants

Where is the solubility product of lead carbonate

            …… (4)

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For mass balance consideration,

                                                        …… (5)

Substitute equations (3) and (4) into equation (5):

                              …… (6)

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Substitute equation (1) into equation (6):

                                                  …… (7)

As is given in the question, , therefore, the concentration of hydronium ions present is

           

So the concentration of hydronium ion is

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Insert all the values in equation (7) to get:

                       

The solubility is directly dependent on the concentration of zinc

           

The solubility of is ( ) equal to the concentration of ions present in the solution.