Re: [Phys-l] two fluids questions

[Bernard Cleyet <bernardcleyet@redshift.com>]

Solubility of gases

Henry's law is used to quantify the solubility of gases in solvents. The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas above the solvent. This relationship is written as:

where kH is a temperature-dependent constant (for example, 769.2 L•atm/mol for dioxygen (O2) in water at 298 K), p is the partial pressure (atm), and c is the concentration of the dissolved gas in the liquid (mol/L).
In the presence of small bubbles, the solubility of the gas does not depend on the bubble radius in any other way than through the effect of the radius on pressure (i.e., the solubility of gas in the liquid in contact with small bubbles is increased due to pressure increase by Δp = 2γ/r; see Young–Laplace equation)[10].
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http://en.wikipedia.org/wiki/Solubility#Pressure


I think there's a misinterpretation here.  The solubility is a function of the pressure of the particular gas, not the total pressure.  So I agree w/ the chem. c.

bc




On 2010, Nov 18, , at 10:38, curtis osterhoudt wrote:

> 1. I suspect your chemistry colleague is simply wrong. Taken to the extreme, his 
> argument that the CO2's partial pressure won't change would indicate the same 
> result whether there's a vacuum above the fizzy drink, or a pure CO2 atmosphere. 
> The suggestion to preserve the fizz by removing the air is absolutely tosh.
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> ________________________________
> From: Anthony Lapinski <Anthony_Lapinski@pds.org>
> To: phys-l@carnot.physics.buffalo.edu
> Sent: Thu, November 18, 2010 11:18:09 AM
> Subject: [Phys-l] two fluids questions
>
> 1. You may have seen a Fizz-Keeper sold in supermarkets. It's a plastic
> attachment you screw onto a plastic soda bottle. You pump it to force air
> into the bottle. This creates a higher air pressure above the soda, so it
> should preserve the soda from going flat. Makes sense. However, my
> chemistry colleague recently informed me that this does not work! He said
> the partial pressure of CO2 will be the same whether you increase the air
> pressure or simply put the cap on. The best way to preserve the fizz would
> be to add CO2 gas, or simply squeeze the bottle to remove most of the air
> and then cap it. Does this make sense? I know physics, but not as much
> chemistry.

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