Absolutely pure carbonic acid does not spontaneously decompose. In the absence of water, the half-life for the decomposition is 180 000 years. But even a single molecule of water catalyzes the rate of decomposition by a factor of fifty billion times.

How does carbonic acid decompose?

Commonly seen as the "fizz" in carbonated beverages, carbonic acid will spontaneously decompose over time into carbon dioxide and water. The reaction is written as: H₂CO₃ → H₂O + CO. Other carbonates will decompose when heated to produce their corresponding metal oxide and carbon dioxide.

At what temperature does carbonic acid decompose?

For water-free carbonic acid, the KIE (i.e., kH2CO3/kD2CO3) for the decomposition reaction is predicted to be 220 at 300 K, whereas it amounts to 2.2-3.0 for the investigated mechanisms including three water molecules. This result is therefore reasonably close to the experimental value of 2 (at 300 K).