- #1
Silversonic
- 130
- 1
First my notes discover that for an isothermal transformation;
ΔW ≥ ΔF
Where W is the work done and F is the Helmholtz Free Energy, F = E - TS.
Then it defines the Gibbs free Energy;
G = F + PV
"For a system at constant temperature and pressure, G never increases";
So ΔG = ΔF + Δ(PV) = ΔF + PΔV = ΔF + ΔW
Then it says "We already know ΔW ≤ -ΔF and therefore ΔW + ΔF = ΔG ≤ 0".
But how can we assume ΔW ≤ -ΔF from the fact that ΔW ≥ ΔF? If ΔW is positive and |ΔW| ≥ |ΔF| then this assumption does not work, and also I have nothing that indicates to me the change in the work done is either positive or negative. I can't seem to show how this proof was meant to work otherwise though, any help?
ΔW ≥ ΔF
Where W is the work done and F is the Helmholtz Free Energy, F = E - TS.
Then it defines the Gibbs free Energy;
G = F + PV
"For a system at constant temperature and pressure, G never increases";
So ΔG = ΔF + Δ(PV) = ΔF + PΔV = ΔF + ΔW
Then it says "We already know ΔW ≤ -ΔF and therefore ΔW + ΔF = ΔG ≤ 0".
But how can we assume ΔW ≤ -ΔF from the fact that ΔW ≥ ΔF? If ΔW is positive and |ΔW| ≥ |ΔF| then this assumption does not work, and also I have nothing that indicates to me the change in the work done is either positive or negative. I can't seem to show how this proof was meant to work otherwise though, any help?