# Physics question- Gas inside beer bottles **URL:** \ **Category:** Factual Questions\ **Created:** [June 20, 2005, 7:52pm UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104 "2005-06-20T19:52:27Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![bizzwire](https://avatars.discourse-cdn.com/v4/letter/b/958977/32.png) [@bizzwire](https://boards.straightdope.com/u/bizzwire)\ **Post date:** [June 21, 2005, 8:59pm UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/21 "2005-06-21T20:59:17Z")
> [@chaoticdonkey](#): > > Nope, CO[sub]2[/sub] and O[sub]2[/sub] take up the same amount of space. Remember the rule that 1 mol of any gas at STP takes up… umm… 22.4L? 23.4L? It doesn’t matter. My point is that it’s the same volume. From the 58th edition of the CRC handbook of chemistry and physics, I offer the following: molecular diameter CO[sub]2[/sub]: 3.34 X 10[sup]-8[/sup] cm O[sub]2[/sub]: 2.98 X 10[sup]-8[/sup] cm coefficient of diffusion in air CO[sub]2[/sub]:0.139 cm[sup]2[/sup]/sec O[sub]2[/sub]:0.178 cm[sup]2[/sup]/sec So, Oxygen is a smaller molecule with a higher diffusivity (in air, at least). I forget…what was the question again? ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [June 21, 2005, 8:59pm UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/22 "2005-06-21T20:59:52Z")
Except that your river was turned into a lake by someone putting up a dam, which you now need to swim through, and the experts are saying you should cover the dam with wax to keep all the swimmers out. I love analogies. 😃 ---
**Author:** ![chaoticbear](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)\ **Post date:** [June 21, 2005, 9:12pm UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/23 "2005-06-21T21:12:28Z")
> [@bizzwire](#): > > From the 58th edition of the CRC handbook of chemistry and physics, I offer the following: > > molecular diameter > CO[sub]2[/sub]: 3.34 X 10[sup]-8[/sup] cm > O[sub]2[/sub]: 2.98 X 10[sup]-8[/sup] cm > > coefficient of diffusion in air > CO[sub]2[/sub]:0.139 cm[sup]2[/sup]/sec > O[sub]2[/sub]:0.178 cm[sup]2[/sup]/sec > > So, Oxygen is a smaller molecule with a higher diffusivity (in air, at least). > > I forget…what was the question again? Yeah, but it doesn’t really matter since a given quantity of either would occupy the same space. I thought the question was whether or not that was true, but I’ve forgotten too. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [June 21, 2005, 9:23pm UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/24 "2005-06-21T21:23:35Z")
Okay, let me see if I have this right: If we are able to cap a bottle with a gas mostly consisting of CO2 in the headspace ( it has more CO2 than the outside air, but less O2 than the outside air) even though the combined gas pressure is inside the bottle is greater than the outside air, the O2 in the ouside air will want to enter the bottle and the CO2 inside the bottle will want to exit. Is this correct? Along with that, some O2 will exit the bottle and some CO2 will enter the bottle because of diffussion? ---
**Author:** ![bizzwire](https://avatars.discourse-cdn.com/v4/letter/b/958977/32.png) [@bizzwire](https://boards.straightdope.com/u/bizzwire)\ **Post date:** [June 22, 2005, 12:35am UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/25 "2005-06-22T00:35:31Z")
> [@chaoticdonkey](#): > > Yeah, but it doesn’t really matter since a given quantity of either would occupy the same space. > > I thought the question was whether or not that was true, but I’ve forgotten too. No, the question was whether one preferentially can permeate a membrane. I think. ---
**Author:** ![bizzwire](https://avatars.discourse-cdn.com/v4/letter/b/958977/32.png) [@bizzwire](https://boards.straightdope.com/u/bizzwire)\ **Post date:** [June 22, 2005, 12:37am UTC](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104/26 "2005-06-22T00:37:40Z")
> [@x-ray vision](#): > > Okay, let me see if I have this right: If we are able to cap a bottle with a gas mostly consisting of CO2 in the headspace ( it has more CO2 than the outside air, but less O2 than the outside air) even though the combined gas pressure is inside the bottle is greater than the outside air, the O2 in the ouside air will want to enter the bottle and the CO2 inside the bottle will want to exit. Is this correct? I say “Yes”, because its not absolute pressurepressure, but _partial_ pressure. [Previous page](https://boards.straightdope.com/t/physics-question-gas-inside-beer-bottles/309104.md?page=1)