units for heat capacity


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Nick_Kopooshian_3C
Posts: 12
Joined: Fri Jul 22, 2016 3:00 am

units for heat capacity

Postby Nick_Kopooshian_3C » Tue Jan 31, 2017 9:40 am

are the units for heat capacity just kJ/C or can they also be kJ/K ?

Katrina_Galian 1J
Posts: 22
Joined: Wed Sep 21, 2016 2:57 pm

Re: units for heat capacity

Postby Katrina_Galian 1J » Tue Jan 31, 2017 10:36 am

It can be both, but C is the standard unit. It's on page 18 of the course reader :)

samuelkharpatin2b
Posts: 55
Joined: Wed Sep 21, 2016 2:57 pm

Re: units for heat capacity

Postby samuelkharpatin2b » Tue Jan 31, 2017 12:12 pm

Celsius is the usual unit used in heat capacity. When talking about specific heat capacity though, the units would be J/(degrees C)(g).

Chem_Mod
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Re: units for heat capacity

Postby Chem_Mod » Tue Jan 31, 2017 10:22 pm

I think I'd like to clear up some confusion on this because there is a lot of conflicting information out there...

The standard unit of heat capacity is J/K. not J/C

You may similarly find molar heat capacity listed in Appendix 2 in the back of the textbook as J/(mol K).
For specific heat capacity the book uses J/(C g) however, if you look elsewhere like for instance wikipedia, specific heat capacities there are tabulated as J/(g K) and in the end, this is okay because it turns out to be a non issue in practice.

Notice.... When calculating the amount of heat exchanged when an object is raised in temperature 10 C, it is also raised in temperature by 10 K. Another way of saying this is that when considering we don't really care what temperature scheme we are working with, because its the same number. It would be a lousy extra step to convert all temperatures into kelivn, only to subtract them to find that is the same number as if we just used Celsius.

So technically speaking, heat capacity is J/K... Practically speaking, For most problems that are using does it matter? No.
If its easier to think of it being J/C then by all means knock yourself out, but typically you will see most quantities expressed in kelvin.

Of course, you never know, maybe it keeps getting used in both ways to confuse gen chem students just a little more

Zoe Robertson 2H
Posts: 28
Joined: Fri Jun 17, 2016 11:28 am

Re: units for heat capacity

Postby Zoe Robertson 2H » Wed Feb 01, 2017 4:42 pm

If in doubt, is it a good idea to use Kelvin instead of Celsius (in general, for all kinds of problems) unless specified otherwise?

Chem_Mod
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Re: units for heat capacity

Postby Chem_Mod » Wed Feb 01, 2017 11:25 pm

I would say generally that is a good rule of thumb, but like any problem you should be very aware of the units that you are using.


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