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Selveste
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Homework Statement
A generalized [itex]TdS[/itex]-equation for systems of several types of "work-parts" and varying number of particles in multiple components, is given by
[tex] dU = TdS + \sum_{i}y_idX_i+\sum_{\alpha =1}^{c}\mu_\alpha dN_{\alpha} [/tex]
Thus, its natural to regard the internal energy [itex]U[/itex] (an extensive property), as a function of the extensive variables [itex] U, S, {X_i}, {N_{\alpha}}. [/itex] Here [itex] U_\alpha [/itex] is the chemical potential for component [itex] \alpha [/itex], and [itex] N_\alpha [/itex] is the number of particles in component [itex] \alpha [/itex] of the system (a number that can vary by [itex] dN_\alpha \neq 0 [/itex]). Thus we have
[tex] U = U(S, X_i, N_\alpha) [/tex]
Because [itex] (U, S, X_i, N_\alpha) [/itex] are all extensive properties, we have the following homogeneity condition
[tex] U(\lambda S, \lambda {X_i}, \lambda {N_\alpha}) = \lambda U(S, {X_i}, {N_\alpha}) [/tex]
Homework Equations
My question regards a special case of this, namely a one-component gass system (not an ideal gass!) with the following internal energy
[tex] U = U(S, V, N) = \frac{aS^3}{NV} [/tex]
where [itex] a [/itex] is a a constant with dimension [itex] K^3m^3/J^2 [/itex].
Problem: find the pressure [itex] p [/itex], the temperature [itex] T [/itex] and the chemical potential [itex] \mu [/itex] of this gas expressed by [itex] (S, V, N) [/itex]. And then find the heat capacities at constant volume [itex] C_V [/itex] and pressure [itex] C_p [/itex], expressed by [itex] (N, T, V ) [/itex] and [itex] (N, T, p) [/itex], respectively.
The Attempt at a Solution
The [itex] TdS [/itex]-equation becomes
[tex] TdS = dU + pdV - \mu dN = C_vdT + \left[\left(\frac{\partial U}{\partial V}\right)_T + p\right]dV - \mu dN[/tex]
But here I am completely at a loss.