The solubility of CaCO3 is pH dependent. (a) Calculate the

Problem 17.99

The solubility of  is pH dependent. (a) Calculate the molar solubility of  1 2 neglecting the acid base character of the carbonate ion. (b) Use the Kb expression for the CO3 2 - ion to determine the equilibrium constant for the reaction

 (c) If we assume that the only sources of Ca 2 + , HCO3 -, and OH- ions are from the dissolution of , what is the molar solubility of  using the equilibrium expression from part (b)? (d) What is the molar solubility of  at the pH of the ocean (8.3)? (e) If the pH is buffered at 7.5, what is the molar solubility of ?

                                                              Step by Step Solution

Step 1 of 5

Molar solubility is the number of moles of a substance that can be dissolved per liter of the solution before the solution becomes saturated. Its S.I Unit is mol / L.

Solubility Product constant   is the equilibrium between a solid and its respective ions in a solution. The value of constant identifies the degree to which the compound can dissociate in water. Higher the solubility product constant more soluble the compound is.

It can be calculated as follows;

Applying law of mass action,  

pOH is a measure of hydroxide ion concentration of a solution. It is calculated as follows;

a)

Molar solubility of a substance is the number of that substance dissolved in one liter of the

solution.

A small molar solubility value means the substance is partially or sparingly soluble. Now, write the equation for dissociation of calcium   carbonate, .

Then  for the above equilibrium is given by the relation;

The ratio between  and  and that between  and       would be 1: 1  This implies that the solution contains same amount of  and

Thus, the molar solubility of carbonate ion, x is

Therefore, the molar solubility of   is .