Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] polytropic Sackur-Tetrode

This formula is more commonly known as the 'spectroscopic entropy'. It is basically the derivative of the free energy in terms of T with V held constant. É© is h/(2 pi m k T)^1/2. The formula differs from yours only by the inclusion of a factor representing the weight of the lowest electronic state, w.

S/N V/N É¡
----- = ln w----- + -----
k É©^3 É¡-1

Wilson: Thermodynamics and Statistical Mechanics, Cambridge, 1960

I highly recommend Schroeder's book (Thermal Physics, 2000). Very accessible to undergraduates.

On page 255 he discusses this kind of thing, but in addition to the electronic "weight" (partition function), he points out you need to include a rotational partition function. And if you heated the gas up very hot, I would suppose you would need a vibrational partition function as well. So I think there are extra terms to include, which is why texts commonly dwell on the monatomic case. -Carl
Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363