# Homework Help: Finding chemical potential with given thermodynamic relation

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1. Nov 2, 2016

### Chan Pok Fung

1. The problem statement, all variables and given/known data
Suppose you are given the following relation among the entropy S, volume V , internal energy U, and number of particles N of a thermodynamic system, where A is a constant.:
$$S = A(NVU)^{\frac 1 3}$$
Find the chemical potential μ(T,P)
2. Relevant equations
$$\frac μ T = -(\frac{∂S}{∂N})_{U,V}$$
U = TS - PV + μN
3. The attempt at a solution
$$\frac μ T = -(\frac{∂S}{∂N})_{U,V} = \frac 1 3 A N^{-\frac 2 3} (VU)^{\frac 1 3}$$
This only solved μ(U,V,N)
Since internal energy is a function of N,V,T : U(N,V,T)
$$∴ μ(U,V,N) → μ(T,\frac V N) → μ(T,P)$$
However, I don't know how to carry out the above transform in this case. I don't know U(N,V,T)

Thanks!

2. Nov 2, 2016

### DrDu

Try to express p and T in terms of U, S and V, using dU=TdS-pdV.
Then set up G(T,p,N)=U-TS+pV.
Calculate mu from G.

3. Nov 2, 2016

### Chan Pok Fung

Oh! Thanks, I didn't think of that before