- #1

zacc

- 8

- 0

**Summary::**Gibbs and Helmholtz energies calculations for heating an ideal gas at constant volume

I am solving a problem involving an ideal gas that undergoes several chained changes of state. One of the steps asks to calculate the change in Gibbs Energy (DeltaG) and Helmholtz energy (Delta A) for 0.1 mol of the gas being heated from 20 oC to 120 oC at constant volume. The initial volume is 4.0 L. I am stuck here.

In natural variables dG is given by dG=VdP-SdT. The first term is easily calculated by replacing V by nRT/P and integrating.The second term is what I don't know what to do with it. Every textbook that I have checked so far have examples where T is constant so the second term is not an issue but not in this problem. The same problem is also found with Helmholtz energy: dA=-PdV - SdT. The first term is zero because dV=0 but then I am stuck again with the second term.

Any help is greatly appreciated!