Conversion between mole fractions and volume fractions in gas analysis 1

[kmac23]

When can you assume that volume percent is the same as mole percent?
I've read in another posting that you can assume this at low pressure but I'd like to know why and under what conditions.


Note: I have already submitted this thread under a different subject and had various replies. thread798-213695

 

[katmar]

The ideal gas equation is PV = nRT. This shows that for an ideal gas V (Volume) is directly proportional to n (number of moles). This makes the volumetric and molar concentrations equal for ideal gases.

For real gases the relationship is PV = nZRT where Z is the compressibility of the gas. Z varies with temperature and pressure, but for "low" pressures and "high" temperatures Z is close to 1.0, and the ideal gas equation basically applies. You need to find out what Z is for your gases under your conditions.

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[dcasto]

kmac23, are you forumn shopping? Why post the question under two different engineering discplines?

 

[kmac23]

Forum shopping? I have only just started using eng tips and didn't realise I'd posted under a different forum. Anyway, a poster on the old thread said to repost under a different heading. I might just delete the old thread actually as I'm happy with the posts