State of carbon dioxide during fermentation

miniradman

1. The problem statement, all variables and given/known data
I know that the process of fermentation occurs in two steps, however, in the second step where glucose/sucrose is broken down into ethanol and carbon dioxide, is the carbon dioxide expelled as a gas or in an aqueous state? (I'm assuming water is involved here)


2. Relevant equations
[itex] C_6 H_12 O_6 _(aq) \rightarrow 2C_2 H_5 OH _(l) + 2CO_2 _(?) [/itex]


3. The attempt at a solution
Well, I'm going to take a stab in the dark and say its in an aqueous state, then escapes as gas as the solution settles down.

chemisttree

Yep. Aqueous carbonic acid.

epenguin

Try to take a trip round a brewery one day. Then you'll see.

Don't fall into the fermentation vat though, it might sound nice but without immediate trained rescue you would soon suffocate. Don't even fall into it after they have opened the plug and taken the beer away.

science_guide

Both chemisttree and epenguin are correct, the CO2 will be dissolved aqueously and then potentially escape out as gas. If you wanted to know exactly how much CO2 will remain dissolved vs. how much will escape, you would have to know the solubility of CO2 gas in the liquid (say, water), and the moles of CO2 that are being created. In the case of fermentation, typically the amount of moles of CO2 created are very high, and easily overpower the solubility of H2O, thus resulting in large amounts of CO2 gas being released. However, the water that the fermentation is taking place in will also be heavily saturated with dissolved CO2. That is why when you open the top off of a soda or beer the dissolved CO2 begins escaping.

EDIT: I should have added that the vapor pressure on top of the liquid will also affect how much CO2 is dissolved vs. escapes as a gas. This is why beer is typically brewed under pressure, increasing the amount of CO2 that is dissolved.