Question

Calcium carbonate is relatively insoluble and the dissolution reaction is endothermic:
CaCO₃(s) ⇌ Ca²⁺(aq) + CO₃^2-(aq). Which change in reaction condition below will shift the equilibrium to the right?

Answer 1

We have to rely on the le chatelier's principle. When a reaction is endothermic we can treat the heat (q) as a reactive, in this way:

q + CaCO3(s)     Ca+2 + CO₃^-2 (endothermic)

So if you increase temperature you are increasing q in the reactants and the system will shift the equilibrium to the right.

Another way to shift the equilibrium to the right is adding acid (H⁺). The H+ added will react with CO₃^-2 to produce CO2 (g) which is removed from the reaction.

CO₃^-2_(aq) + 2H⁺   H₂CO3 CO₂ (g) + H₂O