Expansion work done by/on the system - Problem 8.17

Moderators: Chem_Mod, Chem_Admin

keyanabogan 2J
Posts: 17
Joined: Wed Sep 21, 2016 2:56 pm

Expansion work done by/on the system - Problem 8.17

Postby keyanabogan 2J » Fri Jan 13, 2017 10:06 pm

I'm still having a little a trouble on determining whether expansion work is being done by the system or on the system. On problem 8.17 a) it shows that the system is a liquid and the surrounding is a solid, so does the phase state that the system and the surrounding is in act as an indicator on whether work is done by/on the system?

Also, is it okay to assume that when expansion work is done on the system that w is positive and that when expansion work is done by the system that w is negative?

Anmol Dhaliwal 2C
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm

Re: Expansion work done by/on the system - Problem 8.17

Postby Anmol Dhaliwal 2C » Sat Jan 14, 2017 12:49 pm

The phase state of the system does affect whether work is done on/by the system, such as in a) work is done by the system because there is expansion from a solid to a liquid (liquids are more dispersed in a sense and therefore there is expansion). It is also okay to assume that w is positive when work is done on the system and negative if it is done by the system. (The phase a system changes into indicates whether work is done on or by the system because when converting from solid to liquid, work was done by the system and in b) work was done on the system as it turned from vapor to liquid). Hope this helps!


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 1 guest