Re: CO2, O2 diffusion rates

---------- Forwarded message ----------
From: psears at emr1_NRCan.gc.ca (Paul Sears)
Message-Id: <9702241432.AA14456@emr1.emr.ca>
Subject: Re: CO2, O2 diffusion rates
To: Aquatic-Plants at ActWin_com
Date: Mon, 24 Feb 1997 09:32:34 -0500 (EST)

> From: krombhol at felix_teclink.net (Paul Krombholz)
> Subject: Re: Homework Assignment
> However, I am pretty sure that CO2 also
> diffuses faster, because it can diffuse in several forms (dissolved CO2,
> carbonic acid, and bicarbonate ion).  Chemists: back me up!  I'm too old
> and feeble to look up solubilities and diffusion rates.  Thanks.
	It may diffuse faster, but I'm not impressed by the argument above.
In water, only about 1/500 part of the CO2 exists as carbonic acid, and
the transition reaction is very slow (by chemical standards).  I think
the diffusion of CO2 will be decided by the diffusion of the CO2 itself.
Its higher solubility may help, because you may be able to get a bigger
concentration gradient, and thus faster transport even if the diffusion
coefficient is lower.  It may be lower, the molecular weight of CO2 is
higher, and neither molecule has a dipole.

Paul Sears        Ottawa, Canada

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