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Molar internal energy (4B.3A)

Posted: Sat Feb 08, 2020 6:17 pm
by Malia Shitabata 1F
Can someone walk me through this problem? I'm not sure I understand molar internal energy properly because I'm not getting the right answer when I plug it in:

Estimate the contribution of motion to the molar internal energy of water vapor at 25 ÂșC.

Re: Molar internal energy (4B.3A)  [ENDORSED]

Posted: Sat Feb 29, 2020 4:34 pm
by Chem_Mod
The contribution of motion to the molar internal energy of a water molecule at 25C is the sum of its average rotational and translational energies at that temperature. As described in the passage above the problem, the translational energy is 1.5RT and the rotational energy for a nonlinear molecule (water is bent and therefore nonlinear) is 1.5RT. Added together this is 3RT= 3 * 8.314 J/ mol K * (273 + 25)K = 7.44 kJ/mol