# Gibbs free energy

#### jgalt42

##### Full Member
10+ Year Member
It said on EK that Gibbs free energy is the maximum capacity for a rxn to do non PV work. How do we know something does non-PV work?

#### jgalt42

##### Full Member
10+ Year Member
Does non PV work still move a mass across a distance?

#### G1SG2

##### Full Member
10+ Year Member
5+ Year Member
It said on EK that Gibbs free energy is the maximum capacity for a rxn to do non PV work. How do we know something does non-PV work?

PV work occurs when volume changes, because the equation is actually PdeltaV. If the volume stays the same, then deltaV=0, and no PV work is done. If the volume doesn't change, then it's not PV work.

#### jgalt42

##### Full Member
10+ Year Member
So the volume never changes in a rxn that produces free energy?

#### G1SG2

##### Full Member
10+ Year Member
5+ Year Member
Does non PV work still move a mass across a distance?

Yes because remember, ANY type of work moves an object of some mass across a distance D by means of a force F. This is the definition of work. Work=force*displacement*costheta, with theta being the angle between force and displacement. Any type of work would cause displacement. If not, then there's no work!

#### jgalt42

##### Full Member
10+ Year Member
Thanks,

What is being displaced when there is no volume change if there is still work just not in the form of PV work? The random movements of molecules in the reaction?

#### G1SG2

##### Full Member
10+ Year Member
5+ Year Member
Thanks,

What is being displaced when there is no volume change if there is still work just not in the form of PV work? The random movements of molecules in the reaction?

Whenever I think of PV work, I think of a gas in a container with a piston or something, and compression and/or expansion of that gas which may involve a change in volume. The volume of the system in non-PV work would remain constant. When I think of non-PV work, I think of a box sliding down an inclined plane, where the system is the box and the surroundings are everything else. The entire object would be displaced in non-PV work.

This thread is more than 12 years old.

Your message may be considered spam for the following reasons: