Physics of carbination

[tolbiny]

"I don't want to get into the whole physics of carbination with you, but ..." Jerry seinfeld.

I've been drinking and reading the airplane thread in OOT and it reminded me of an old argument with my older brother.
I find an open 2 liter of pop (soda for some of you) with the cap sitting next to it. So i put the cap back on the 2 liter (litre for some of you). The villan comes in yell sat me saying he left it open on purpose cause he was going to have another glass (cup for some of you) shortly. He contends that repeated closing and opening of the bottle releases carbination faster that leaving it open. I contend thatthe carbination released while the bottle is closed will be trapped, increasing the pressure above the remaining soda, keeping more carbination within the soda itself.

[BluffTHIS!]

H2O + CO2 <--> H2CO3

Here's the chemistry of it. I believe the physics would involve pressure, volumes, temperature and entrophy but I mostly slept through thermo.

[bobman0330]

You're right, brother is wrong.

When the cap is on, the dissolved CO2 comes to equilibrium with the CO2 in the air in the bottle. When the cap is off, CO2 is constantly bleeding out. The rate of gas "undissolving" is inversely proportional to the pressure of CO2 above the liquid. With the cap off, P(CO2) will always be lower, so rate is higher, and more CO2 is lost over any time period.

[ThinkQuick]

Over a longer period of time, of course yo are correct, as anyone knows you must cap a bottle of pop to prevent it from losing its carbonation.

However, over a small period of minutes, there will be a minimal amount of equilibration / loss of carbon dioxide.

Picking up the bottle and moving it about as you replace the cap could easily introduce more fresh air and mix it with the pop, causing a much more rapid loss of carbon dioxide. This is probably not offset by the extra few minutes the bottle spends closed. Even if the difference is significant I think the effect will be minimal and certainly not worth yelling about.

Note however, if the cap is indeed lying beside the bottle and you replace it in a nonviolent way, then as bobman says, this will certainly keep the pop carbonated longer

[Slim Pickens]

The carbonation will be released more slowly with the cap periodically on rather than left off. Your brother will be more likely to notice the loss of carbonation when the bottle hisses at him as he re-opens it.

The real question is what would happen if you put a 12oz can of carbonated beverage in a centrifuge for a while and then opened it. Don't try calling the Coca-Cola "Questions and Comments" phone number either because they are absolutly no help on that one.