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Topic: Why is the universal gas constant 0.08206?  (Read 19411 times)

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Offline confus3d

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Why is the universal gas constant 0.08206?
« on: September 26, 2007, 06:12:59 PM »
How was that derived? by whom?
What were the calculations?

Offline Borek

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Re: Why is the universal gas constant 0.08206?
« Reply #1 on: September 26, 2007, 06:44:28 PM »
It is determined experimentally.

0.08205783 L*atm/(K*mol)
8.314510 kPa*dm3/(K*mol)
8.314472 L*kPa/(K*mol)
8.314472 J/(mol*K)
62.3637 L*mmHg/(K*mol)
83.14472 L*mbar/(K*mol)
1.987216 cal/(K*mol)
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Offline pantone159

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Re: Why is the universal gas constant 0.08206?
« Reply #2 on: September 27, 2007, 02:59:53 AM »
Another way of looking at it, is that the 'gas constant' is Boltzman's constant, k, from statistical mechanics, times Avagadro's number.  R = k * Na.  (Physicists like to count by single things, chemists like to count by moles.)

How the value of k is determined, I leave as an exercise for the reader.  :)

Offline billnotgatez

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Re: Why is the universal gas constant 0.08206?
« Reply #3 on: September 29, 2007, 07:29:51 PM »
If you treat this as an algebraic problem it seems somewhat clearer.

PV=nRT is rearranged to R=PV/nT
You also know that 1 mole has a finite volume at standard temperature and pressure
1 atmosphere pressure
273.15 K temperature
1 mole
Approximately 22.4 liters (let us use 22.4140962645)
Therefore 0.08205783 = 1 * 22.4140962645 / 1 * 273.15

I think that the confusion comes in when you use just 22.4 and get a slightly different value for R.


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