Thermodynamics problem; App of 1st law, work, adiabatic processes, and enthalpy

[ChronicQuantumAddict]

The question is as follows:

the partial derivative (given as a partial, but i dont know the notation, so letter d is really little delta for the partial)

(du/dT)p = Cp - P(Beta)v

where Beta = expansivity coefficient = 1/v (dv/dT)p

again, all the "d's" are lowercase delta's for the partial derrivatives, and the "p's" next to the partials and the one with the Cp are to signify that pressure is constant.

I know i need to start with enthalpy, dh, but im pretty much stuck. if someone would point me in the right direction i would be much obliged. thanks :devil:

[Astronuc]

It appears that one is trying to show the relationship:

(du/dT)p = Cp - P(Beta)v

or

(\frac{\partial u}{\partial T})_p = c_p - p\beta v

where

\beta = \frac{1}{v} (\frac{\partial v}{\partial T})_p


OK, how about starting with h = u + pv , or

u = h - pv

differentiating with respect to T at constant P,

(\frac{\partial u}{\partial T})_p = (\frac{\partial h}{\partial T})_p - (\frac{\partial (pv)}{\partial T})_p

and go from there remembering the definition of c_p is

c_p = (\frac{\partial h}{\partial T})_p

[ChronicQuantumAddict]

duh, thank a lot. i see it clearly now. much thanks

[Astronuc]

I have those moments too. :biggrin: