Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: a confused chiral girl on January 25, 2007, 11:11:36 PM
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Hi, I am having trouble with this problem --> 0.39 litre of an ideal monatomic gas (Cv = 3R/2) initially at 59 deg C and 2.3 atm pressure undergo an expansion against a constant external pressure of 1.13 atm, and do 2 kJ of work. The final pressure of the gas is 1.13. Calculate the change in enthalpy, Delta H.
I used deltaH = nCpdT, and found n, Vfinal, and T final. but I am not getting the correct answer which is supposed to be 4884 J .
Please show me the steps to this question, instead of dropping hints if possible. I need to know the steps for tomorrow's test. Thank u very much!! :-*
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The equation you are using is correct. The first thing I would say to check is your units (because you did not show your actual work, or steps, I can only guess).
The reason I say so is, because you said the answer should be 4884J, enthalpy is usually given in kJ.
So the question is, what are you using for R and what are the units of R?
Do they cancel properly? Are you using the correct R that will work with liters and atm, or did you convert those units?
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What value are you using for Cp?