What is the relationship between entropy and pressure in thermodynamics?

In summary, the conversation discusses finding the partial derivative of H with respect to P in terms of P, V, T, β, κ, and c_p. The conversation includes several equations and the speaker mentions being stuck and unsure how to proceed. The expert suggests starting with the exact differential dG=-SdT+VdP and using the equation Tds = dh - vdp to find the desired partial derivative.
  • #1
happyparticle
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Homework Statement
Derive ##(\frac{\partial H}{\partial P})_t## in term of ##P,V,T, \beta, \kappa, c_p##
Let H = H(T,P)
Relevant Equations
##ds = (\frac{\partial S}{\partial H})_p dH + (\frac{\partial S}{ \partial P})_H dP##

##dH = (\frac{\partial H}{\partial T})_p dT + (\frac{\partial H}{ \partial P})_T dP##
Hi,
Starting from dS in term of H and P, I'm trying to find ##(\frac{\partial H}{\partial P})_t## in term of ##P,V,T, \beta, \kappa, c_p##.
Here what I did so far.

##ds = (\frac{\partial S}{\partial H})_p dH + (\frac{\partial S}{ \partial P})_H dP##

##ds = (\frac{\partial S}{\partial H})_p [ (\frac{\partial H}{\partial T})_p dT + (\frac{\partial H}{ \partial P})_T dP] + (\frac{\partial S}{ \partial P})_H dP##

##\frac{\partial S}{\partial P} = (\frac{\partial S}{\partial H})_p (\frac{\partial H}{\partial T}) (\frac{\partial T}{\partial P}) + (\frac{\partial H}{\partial P})_T (\frac{\partial S}{\partial H})_P + (\frac{\partial S}{\partial P})_H##

##(\frac{\partial S^2}{\partial T \partial P}) = (\frac{\partial S}{\partial H})_p (\frac{\partial H}{\partial T}) (\frac{\partial T}{\partial P}) + (\frac{\partial H}{\partial P})_T (\frac{\partial S}{\partial H})_P + \frac{d}{dP}(\frac{\partial S}{\partial P})_H##

##(\frac{\partial H}{\partial P})_T = -(\frac{\partial H}{\partial S})_P (\frac{\partial S}{\partial H})_P (\frac{\partial H}{\partial T})(\frac{\partial T}{\partial P})##

From there, I'm stuck. I don't see how I can get ##P,V,T, \beta, \kappa, c_p##

Thank you
 
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  • #2
Start with the exact differential dG=-SdT+VdP, which means that $$\left(\frac{\partial S}{\partial P}\right)_T=-\left(\frac{\partial V}{\partial T}\right)_P$$
 
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Likes vanhees71
  • #3
I have to start with ds in term of dh and dp.
I just saw in the original post, those P should be in index.

I finally found something using ##Tds = dh - vdp##
 
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