# Change in Enthalpy with no Heat Exchange?

1. Dec 13, 2011

### Zenderson3

This is a rather general question but I'm studying for my thermodynamics final and wanted to clarify this topic.

Is it possible for there to be a change in entropy in a cycle without a net exchange of heat into or out of the system? If so what may be some of the examples of this and how would (if you can) would you calculate this change.

I know the principle of maximum entropy describes that a system would evolve to the equilibrium point of maximum entropy but would it do this if it were adiabatic or does the change in internal energy need to remain constant?

Also I know that if a process is non-quasistatic and adiabatic the entropy will change but is there anyway to calculate this value?

2. Dec 13, 2011

### Andrew Mason

In one complete cycle, a system returns to its original state. So its entropy must be the same. (did you mean enthalpy or entropy in your title?)

No sure what you are getting at. Can you give an example?

Sure. ΔS = ∫dQrev/T

You just need to determine the reversible path between the beginning and end states and calculate the integral along that path.

AM