Isobaric Process, finding Change in Internal Energy

AI Thread Summary
The discussion focuses on calculating the change in internal energy (ΔIE) of nitrogen gas (N2) during an isobaric process. The formula used is ΔIE = (3/2)nRΔT, which accounts for the change in kinetic energy based on temperature change. The calculation yields a result of 3,049.29 Joules for the internal energy change. However, it is noted that this formula only considers translational kinetic energy, while N2, being a diatomic molecule, also has rotational energy contributing to its internal energy. The correct approach should include both translational and rotational contributions to accurately determine ΔIE.
yaylee
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Homework Statement



Assume nitrogen gas (N2) is an ideal gas. n = 7.57 moles of N2 gas are heated isobarically (at constant pressure) from temperature To = 18.6 oC to temperature Tf = 50.9 oC. Find:

c) ΔIE, the change in internal energy of the N2 gas

Homework Equations



Change in IE = Change in KE = (3/2)nRΔT

The Attempt at a Solution



Since this is an ideal gas, only Kinetic Energy considerations need to be accounted for, or,
Change in KE = Change in IE = (3/2)(7.57)(8.314)(50.9-18.6) = 3,049.29 Joules

Once again, thanks for the help! I think I am doing the correct thing, or am I going crazy? =)
 
Physics news on Phys.org
The internal energy of the two-atomic ideal gas contains not only the translational KE, but also the energy connected to rotation. Generally, the internal energy of ideal gases is f/2 nRT where f is the degrees of freedom, 5 for a two-atomic molecule.

ehild
 
(3/2)nRΔT accounts for only the change in translational KE of the molecules. N2 is not a monatomic gas, so the molecules can have additional motion besides translational motion.
 
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