Water vapor in CO2 - a chemical reaction?

I am doing some work on measuring water content of a stream of CO2 at ambient temperatures (25°C).


My question is this: Am I dealing with purely a mixture of gases, or is there some chemical reactions involved? If so, to what degree? I assume there is a reversible reaction to H2CO3


If this is the case, it might alter the measurements.
Analysis techniques include optical and microwave




We will not get a significant reaction in a low-density gas phase; the gas mixture is essentially $\ce{H2O + CO2}$. [Carbonic acid can be made](https://en.wikipedia.org/wiki/Carbonic_acid), but not by reaction of carbon dioxide with water at ambient pressure.


Carbon dioxide does react slightly with liquid water to form a small amount of $\ce{H2CO3}$. But the ability to form this acid at all from carbon dioxide and water depends on the hydrogen bonding between its hydroxyl groups and surrounding water molecules. That requires the water to be densely packed in the medium, which in ordinary conditions means not in the gas phase.


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