Homework help on 8.29

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John Huang 1G
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Homework help on 8.29

Postby John Huang 1G » Sat Jan 13, 2018 6:41 pm

8.29 Which molecular substance do you expect to have the
higher molar heat capacity, NO or NO2? Why?

My question is, can we follow the line of reason that because NO2 has more bonds than NO, we can expect NO2 to require more energy to break bonds; thus resulting in a higher molar heat capacity in NO2?

Bansi Amin 1D
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Re: Homework help on 8.29

Postby Bansi Amin 1D » Sat Jan 13, 2018 7:08 pm

Your reasoning makes sense. NO2 is more molecularly complex than NO so it would have a higher molar heat capacity.

John Huang 1G
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Re: Homework help on 8.29

Postby John Huang 1G » Sat Jan 13, 2018 8:18 pm

Nevermind, I have found a better reason for this phenomenon. It is true that molar heat capacity increases with molecular complexity; but apparently, my initial reasoning was incorrect.

Molar heat capacities of gases composed of molecules are higher than those of monatomic gases because the molecules can store energy in multiple types of kinetic energy (e.g. rotational kinetic energy, translational kinetic energy).

With this line of reasoning, we can infer that because NO2 has more molecules than NO, NO2 is better "equipped" to store energy. Therefore NO2 stores more energy than NO and has a higher molar heat capacity.

204918982
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Re: Homework help on 8.29

Postby 204918982 » Sun Jan 14, 2018 1:57 pm

So thinking in terms of which one has more bonds is incorrect?

Bansi Amin 1D
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Re: Homework help on 8.29

Postby Bansi Amin 1D » Sun Jan 14, 2018 10:36 pm

Ah, so yes. Thinking in terms of number of bonds is incorrect. It's all about the potential to store energy then. That's cool.


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