Explain why calcium carbonate is unable to dissolve appreciably in water.

Answer 1

The main explanation would have to do with the lattice energy (enthalpy) and the hydration enthalpy. Calcium carbonate, CaCO₃ would dissociate to Ca²⁺ and CO₃^2- and so would have quite a large LE (based on the charge) and the enthalpy of hydration wouldn't be enough to overcome the LE. This is an oversimplification, but hopefully answers the question sufficiently.