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Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 2:30 am
by Tiffany Chao 2H
In my notes, it says that it's because delta U = 3/2(nR*delta T) and if delta T = 0, then delta U will be 0. I can understand that logic but where did that delta U = 3/2(nR*delta T) equation come from? And why is it 0?

Thanks

Re: Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 8:06 am
by christabellej 1F
U would equal 0 because it is an isothermal reversible equation, as the internal energy of the system does not change overall.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 8:46 am
by Christineg1G
For an isothermal reaction, the temperature is constant so the internal energy would also be constant (delta U=0).

Re: Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 11:42 am
by Jessica Li 4F
Delta U is 0 for an isothermal reaction because it is a state function and overall everything cancels out. This means that q + w = 0.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 1:09 pm
by Eva Zhao 4I
To add on, I believe the 3/2 in your equation came from 'Ideal gas, Cv = (3/2) R' (which can be found on the formula sheet). Note that this 'C' value varies depending on what you're trying to solve for, i.e. 'Ideal gas, Cp = (5/2) R'.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Mon Feb 10, 2020 5:33 pm
by Joanne Lee 1J
Delta U is zero for isothermal reactions because the internal energy of the system does not change.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Thu Feb 13, 2020 10:53 pm
by Kyle Rex 1K
since its isothermal it means energy cannot come in or leave, so by nature the change in energy would be zero

Re: Why is delta U = 0 for isothermal reactions?

Posted: Thu Feb 13, 2020 11:14 pm
by Harry Zhang 1B
In an isothermal process, the average kinetic energy of the molecules stay the same and since there is no force between the molecules, the potential energy also stays the same. Therefore, delta U=0.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Fri Feb 14, 2020 10:13 am
by Astrid Lunde 1I
U is equal to 0 because it is an isolated system so there is no energy energy leaving or going into the system.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Fri Feb 14, 2020 10:14 am
by Zoe Gleason 4F
The temperature is constant, and no energy will enter or leave the system. Therefore, ΔU=0.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Sun Feb 16, 2020 12:53 pm
by Ying Yan 1F
An isothermal system is one where no heat nor matter is transferred externally, meaning that the energy will always stay the same in the system. That is why U=0 in an isothermal reactions.

Re: Why is delta U = 0 for isothermal reactions?

Posted: Sun Mar 01, 2020 9:41 pm
by Anish Natarajan 4G
Delta U is the change in internal energy of a system, which is dependent on its temperature. If T=0 then Delta U=0