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Fdonovan 3D
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Joined: Sat Aug 17, 2019 12:16 am


Postby Fdonovan 3D » Sat Feb 08, 2020 3:36 pm

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure (b) at constant volume. Treat the gas as ideal.

Looking at the answer key, it says to use n(5/2 R) delta T and n(3/2 R) delta T respectively to solve this problem. However, I don’t remember learning either of these things in class. Do we need to do know these??

Ellen Amico 2L
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Joined: Thu Sep 19, 2019 12:16 am

Re: 4C.3

Postby Ellen Amico 2L » Sat Feb 08, 2020 4:23 pm

My TA mentioned this in discussion and said that at constant pressure for an ideal gas, specific heat (Cp) = 5/2R. At constant volume for an ideal gas, Cv=3/2R. So for part a you would plug in 5/2R into q = nCp∆T and for part b you would plug in 3/2R into q = nCv∆T.

Sartaj Bal 1J
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

Re: 4C.3

Postby Sartaj Bal 1J » Sat Feb 08, 2020 6:38 pm

Since Kr is a single atom, the above values are appropriate for this question. If the molecule is linear, Cv=5/2R and Cp=7/2R. If the molecule is non-linear, Cv=3R and Cp=4R. This is usually done under ideal gas conditions.

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