Final answer:
The CO₂ molecule reacts with water to form carbonic acid, which ionizes to give hydrogen carbonate and hydrogen ions.
Step-by-step explanation:
Once dissolved in water, the CO₂ molecule reacts with water to form carbonic acid (H₂CO₃), which can further ionize to produce hydrogen carbonate (bicarbonate, HCO₃⁻) and hydrogen ions (H+). This reaction is facilitated by an enzyme called carbonic anhydrase, which can convert about a million CO₂ molecules per second. The overall reaction can be represented as CO₂ + H₂O → H₂CO₃ → HCO₃⁻ + H+. However, without the enzyme, the reaction proceeds at a much slower rate.