Science Fair Project Encyclopedia
Activity coefficients
Activity coefficients for chemicals in a mixture are an indicator of what the concentration of that chemical will be in a vapor of the mixture.
In an ethanol/water mixture that is less than 95% ethanol, the activity coefficient for ethanol is higher than water. Therefore the concentration of ethanol in the vapor from the liquid will be higher than in the liquid itself.
At 95% ethanol, the activity coefficients are the same, meaning that the vapor is also 95%. This is called an azeotrope.
Above 95% ethanol, the activity coefficient for water is higher than ethanol, so the fraction of water will be higher in the vapor than in the liquid.
Last updated: 06-07-2005 01:25:52
10-26-2009 08:16:03
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details