# Homework Help: Final Equilibrium Temperature

1. Jan 3, 2012

### sodaboy7

1. The problem statement, all variables and given/known data
An adiabatically isolated system consists of 1 mol of a diatomic gas 100K and 2 mol of a solid at 200K separated by a rigid adiabatic wall. Find the equilibrium temperature of system after adiabatic wall is removed, assuming that the solid obeys the Dulong-Petit law.

2. Relevant equations
mgascgas(T-100) = msolidcsolid(200-T)

mgascgas = Qgas = 5/2 nRT ( 5 is degree of freedom, I guess so)

3. The attempt at a solution

5/2 nRT = Q = msolidcsolid(200-T)

171K

2. Jan 3, 2012

### Redbelly98

Staff Emeritus
I agree with that answer, though you didn't really show how you got it. You haven't shown how you used the Dulong-Petit law, and msolid shouldn't be part of the calculation.

3. Jan 3, 2012

### sodaboy7

The answer was given on back pages of the book. I have not got any answer yet. I dont know how they got that answer.

4. Jan 4, 2012

### Redbelly98

Staff Emeritus
What does your book or class notes say about the Dulong-Petit law? You should look that up, it relates the energy of the solid and its temperature change.