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Ideal gas problem? Rate Topic: -----

#1 24 January 2012 - 05:54 AM Chap 


Quark
I know the ideal gas equation (and how to derive it):PV= (1/3) x N x m x (U)^2 where: P-Pressure, V-Volume, N- number of molecules, m- mass, U- mean speed of molecules. The problem is my book gives a "different" version of the equation:PV= (1/3) x n x M x (U)^2 where: P-Pressure, V-Volume, n- number of moles, M- relative molecular mass, U- mean speed of molecules It goes on explain that: the relative molecular mass (M) of any substance expressed in grams contains the Avogadro constant number of molecules.
That is: M = m x (Avogadro constant).

Is this equation (and explanation) correct? I can't find a website which gives a suitable explanation. Can anyone please give me a link or any useful information?Thanks.

This post has been edited by Chap: 24 January 2012 - 06:09 AM

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#2 24 January 2012 - 06:14 AM hypervalent_iodine 


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Perhaps I'm missing something here, but the ideal gas equation I've always seen is written as PV=nRT.
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#3 24 January 2012 - 06:38 AM Chap 


Quark

View Posthypervalent_iodine, on 24 January 2012 - 06:14 AM, said:

Perhaps I'm missing something here, but the ideal gas equation I've always seen is written as PV=nRT.


yes, you're right, PV=nRT is the ideal gas equation., but that equation I gave is used in deriving the ideal gas equation, is it not?

is that it? Am I looking in the wrong direction?
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#4 24 January 2012 - 06:38 AM DrRocket 


Primate

View PostChap, on 24 January 2012 - 05:54 AM, said:

I know the ideal gas equation (and how to derive it):PV= (1/3) x N x m x (U)^2 where: P-Pressure, V-Volume, N- number of molecules, m- mass, U- mean speed of molecules. The problem is my book gives a "different" version of the equation:PV= (1/3) x n x M x (U)^2 where: P-Pressure, V-Volume, n- number of moles, M- relative molecular mass, U- mean speed of molecules It goes on explain that: the relative molecular mass (M) of any substance expressed in grams contains the Avogadro constant number of molecules.
That is: M = m x (Avogadro constant).

Is this equation (and explanation) correct? I can't find a website which gives a suitable explanation. Can anyone please give me a link or any useful information?Thanks.


Your two equations are equivalent. They are also equivalent to PV=nRT.

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#5 24 January 2012 - 08:16 AM Chap 


Quark
Thanks. However M should stand for "molar mass" right? Not "relative molecular mass", in the second equation?
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