The reaction of water (H₂O) and carbon dioxide (CO₂) is a reversible reaction that forms carbonic acid (H₂CO₃):

H₂O + CO₂ ⇌ H₂CO₃

Here's why it's a reversible reaction:

* Forward reaction: Water and carbon dioxide react to form carbonic acid. This happens in the presence of water, such as in rainwater or in the blood.

* Reverse reaction: Carbonic acid can decompose back into water and carbon dioxide. This process is favored in the presence of heat or in a low pH environment.

Additional details:

* The reaction is also classified as a hydration reaction because water is added to carbon dioxide.

* Carbonic acid is a weak acid that readily dissociates in solution to form hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). This process contributes to the acidity of rainwater and the buffering capacity of blood.

So, while the reaction is often described as forming carbonic acid, it's important to remember that it's an equilibrium reaction that exists in both directions.