Chemistry lime cycle?

Hello, I only have what is written below, but I did not understand it 100% and would need an explanation to the questions

What is the equilibrium reaction in relation to the calcium cycle?

CaCO3 + H2CO3 <=> Ca2+ + HCO -3 , exothermic

What and why is balanced here and is there an imbalance/equilibrium?

And what is the law of mass action with regard to the calcium cycle?

– defines chemical equilibrium for chemical reactions

– describes the relationship between products and reactants

– further reactions take place in equilibrium

– applies to any reaction that is reversible and has already reached equilibrium

K= C (CaH2CO3) / C(CaCO3) • C(H2O) • C(CO2)

Thank you in advance