I performed an experiment to determine the thermodynamic of Ca(OH)2 solubility i

Question

I performed an experiment to determine the thermodynamic of Ca(OH)2 solubility in water. I have the following questions:

Calcium carbonate CaCO3 is less than 1/100th as soluble in water as Ca(OH)2 at room temperature. Carbon dioxide CO2 is a component of air that readily dissolves in water.

1.) Write a chemical equation representing the reaction aqueous Ca(OH)2 with dissolved CO2.

2.) Why should you boil the water for your high temperature determinations for several minutes before adding the solid Ca(OH)2?

3.) In what way, if any, is the temperature dependance of the molar solubility of Ca(OH)2 unusual?

Explanation / Answer

1) CO2 + Ca(OH)2 --> CaCO3(s) + H2O(l)

2) Boiling the water before the addition of Ca(OH)2 will reduce the solubility of CO2 and "drive off" the dissolved CO2, allowing Ca(OH)2 to dissolve without reacting with dissolved CO2.

3) Usually, solubility will increase with increasing temperaturebut after a certain point when CO2 has been almost completely driven off its solubility starts to saturate

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