First Law

Moderators: Chem_Mod, Chem_Admin

JamesAntonios 1E
Posts: 70
Joined: Fri Sep 29, 2017 7:04 am

First Law

Postby JamesAntonios 1E » Tue Feb 13, 2018 2:52 pm

So delta U is 0 when it is an isothermal, reversible expansion. However, what if the expansion is irreversible? Is it still zero? Also, when is q in the first law zero?

Posts: 19582
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 888 times

Re: First Law

Postby Chem_Mod » Tue Feb 13, 2018 5:54 pm

Delta U = 0 for an isothermal process, because internal energy of an ideal gas only depends on the temperature. It doesn't have to be reversible for this to hold true.
Q is zero when we don't supply (or lose) any heat in the process we study.

Sophie 1I
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Re: First Law

Postby Sophie 1I » Sat Feb 17, 2018 1:28 pm

q is zero when there is no heat lost or gained. In the isothermal system q is equal to -w

Jessica Benitez 1K
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: First Law

Postby Jessica Benitez 1K » Sun Feb 18, 2018 2:40 pm

When we have an adiabatic system q=0 and delta U=w because in an adiabatic system there is no heat flow.

Jaewoo Jo 2L
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

Re: First Law

Postby Jaewoo Jo 2L » Sun Feb 18, 2018 8:59 pm

delta U would also be zero in an isolated system or any system that doesn't transfer heat.

Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: First Law

Postby AlyssaPeckham1A » Sun Mar 18, 2018 4:07 am

If no heat is transferred, then q will be equal to zero. This also means that delta U will now be equal to work.

Return to “Thermodynamic Systems (Open, Closed, Isolated)”

Who is online

Users browsing this forum: No registered users and 1 guest