Find molar mass and number of degrees of freedom from heat capacities.

vendredi 2 mai 2014

Hey having a bit of trouble with this one. I really don't know how to start. Think I just simply don't have the right equations or I'm using the wrong units. Hopefully you guys can help me.



1. The problem statement, all variables and given/known data



Find the molar mass and the number of degrees of freedom of molecules in a gas with known heat capacities: Cv = 650 J/(KgK) and Cp=910 J/(KgK).



2. Relevant equations



The equations that I can find in my book that I've been trying to figure out are :



1.Cv = (RP)/2 where R = Gas constant and P = number of degrees of freedom.



2.Cp = R(1+P/2)



3.Cp = Cv + R



3. The attempt at a solution



Well when I first started off I simply applied the Cv formula to the value of Cv and solve for P, the number of degrees of freedom. However when I did this, i got an answer of ~156 which I can immediately tell is not correct.



I am led to believe that I'm not using the correct units for Cv and Cp as they don't solve the last equation(3) correctly.





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