# Homework Help: Isobaric Process, finding Change in Internal Energy

1. Dec 16, 2012

### yaylee

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

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

2. Relevant equations

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

3. 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? =)

2. Dec 16, 2012

### ehild

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. Dec 16, 2012

### TSny

(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.