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Old 01-15-2016, 03:43 PM   #66
mdm
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Quote:
Originally Posted by justatroll View Post
R is a universal constant.
It does not change no matter what.
The only difference you will find for the value R is based on what units you are using, NOT what gas you are using.


It would be like saying that "G" varies based on what material is falling.


Maybe I am the one that is confused....

My understanding (possibly wrong) is that the universal gas constant describes an ideal gas, but there is also individual gas costnat (http://www.engineeringtoolbox.com/in...ant-d_588.html) which describes how an actual gas would behave. But I might be wrong when using it in the same equation.




Now, if we assumed your point of view that we should use the universal R no matter what gas we are considering, and that n is very similar between the gases (because for most gases the volume of one mole under standard conditions is close to "ideal" 22.4 litres), that would mean that the differences between temperature-related pressure changes between gases are far smaller than I calculated. Because it was the difference in R_individual that was responsible for the bulk of the effect.


(Also, I realized that I used the volume of one mole (22.4 to 24.5 L/mol) in place of n (the amount in moles), obviously I should have used the reciprocal of the volume, but it has little effect on the result as again it is R that largely determines the effect.
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