relation between internal energy and enthalpy

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Jessica Yang 1J
Posts: 55
Joined: Fri Sep 29, 2017 7:03 am

relation between internal energy and enthalpy

Postby Jessica Yang 1J » Tue Jan 23, 2018 10:26 pm

I know that the equation is change in enthalpy = change in internal energy - work, but can someone conceptually explain why when work is done by the system (therefore, volume expands) why enthalpy is greater than internal energy? and vice versa for when work is done on the system?

Thanks!

Sarah Rutzick 1L
Posts: 50
Joined: Tue Oct 10, 2017 7:13 am

Re: relation between internal energy and enthalpy

Postby Sarah Rutzick 1L » Tue Jan 23, 2018 10:32 pm

When work is done by the system, the sign for work is negative. Therefore, by subtracting the negative amount of work from the change in internal energy (so basically adding), the enthalpy will be greater than the change in internal energy. When work is done on the system, the sign for work is positive, so by subtracting this positive number from change in internal energy will result in an enthalpy lower than the change in internal energy.


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