[vdemas]

OK, so here's the question:

a) Given that mu = 0.25 K/atm for Nitrogen, calculate the value of   its isothermal Joule-Thomson coefficient.

b) Calculate the energy that must be supplied as heat to maintain constant temperature when 15,0 mol N₂ flows through a throttle in an isothermal Joule-thomson experiment and the pressure drop is 75atm.


This is what I got so far :

mu_T = - C_p . mu

Now, the value of mu is given in the Question.
What I would like to know is how do I calculate C_p ?
Can I assume that C_p = 5/2 R ? Since nitrogen is a monoatomic gas.
So, mu_T = - ( 5/2 ) (8.314510 J/K.mol) x (0.25K/atm)
                                       = - 5,1966J/atm.mol

But at the back of the book the answer is -7,2 J/atm.mol.
How did they get to this?

[leo1]

You should note that nitrogen is a diatomic gas (N2) and hence cp=7/2 *R.

I hope this helps.

[vdemas]

Thanx, I figured that out just after I posted the question.
I feel so stupid.