Equation Explanation

Moderators: Chem_Mod, Chem_Admin

Posts: 10
Joined: Fri Jul 15, 2016 3:00 am

Equation Explanation

Postby Ariana_Kermani_2G » Wed Feb 01, 2017 11:28 pm

Does the equation delta S=q/T only apply to ideal gases? Or does it apply to any isothermal, reversible process?

Also, are there any differences between the equations delta S=q/T and delta S=q(rev)/T?


Posts: 18676
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 611 times

Re: Equation Explanation

Postby Chem_Mod » Wed Feb 01, 2017 11:33 pm

Hi Ariana,

The equation assumes that temperature is constant - a reversible, isothermal expansion/compression. As such, you can only use this equation, and , for an isothermal expansion/compression.

Note that, even if you don't have an isothermal expansion (say both temperature and volume increases), because entropy is a state function, you can turn the expansion into a two-step process (an isothermal expansion and isovolumetric expansion) so that you can use your formulas.

Hope this helps!

Return to “Concepts & Calculations Using Second Law of Thermodynamics”

Who is online

Users browsing this forum: No registered users and 2 guests