In a bottle of unopened cola, the CO2 dissolved in the liquid is in equilibrium with the CO2 gas above the liquid. The dissolved gas reacts with water molecules in the liquid to from carbonic acid, which also dissociates into carbon dioxide and water. Which chemical equation(s) best describe this equilibrium system?

Answer 1

Divided it to two equations.
The first one is turn co2(g) into co2(eq) in liquid.
The second one is reaction between co2(aq) and H2O to produce H2co3

The equation:-
co2(g)--> co2(eq)and co2(eq)+H2O--> H2co3