Contributions to thermodynamics: The inconsistency of

Abstract. Presents a flawed thermodynamic argument to test readers' insight and ingenuity. Keywords (Audience):. Upper-Division Undergraduate. Keyword...
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CONTRIBUTIONS TO THERMODYNAMICS: THE INCONSISTENCY OF THERMODYNAMICS

IN THIS note it will he shown that thermodynamics, heretofore considered to be the most rigorous of all physical disciplines, contains a fatal inconsistency. Although this has long been suspected to he the case by the average student, to the author's knowledge no truly logical argument has been given before to this one. The argument is as follows. If we suppose that thermodynamics is valid and are able to deduce only a single false statement, then by reducto ad absurdurn thermodynamics must he inconsistent. Therefore let us assume the validity of thermodynamics and choose the following example.' Let 1 liter of an ideal gas a t 10 atm. e x ~ a n dfreelv against a constant nressure of 1 "

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'Adapted from problem No. 4, p. i 6 , PRU~TON, C. F., AND S. H. MAEON,"Fundamental Principles of physical chemistry," rev. ed., The MaeMillan Co., New York, 1951. E D I ~ RNOTE: 's This is another in the series of articles by an unknown "Dr. McQuirg," to test our readers' insight and ingenuity. After trvina to find out what is the with his reasining, turn to the comment an page 98.

VOLUME 34, NO. 2, FEBRUARY, 1957

atm. until the final pressure is 1 atm., the whole system being contained in a thermostat a t 298'. The final volume will be 10 liters. Since the gas expands against a constant pressure, w = PAV = 1 (10 - 1 ) = 9 1.-atm. It is well k n o m that for such processes with PV work only, AH = q,. Now the change of state is equivalent to the isothermal expansion of the ideal gas, for which AE = 0 by definition. Hence q = w = 9 1.-atm., and thus AH = 9 1.-atm. But in the isothermal expansion of an ideal gas, A(PV) = 0, whence AH = A E A(PV) = 0. But 9 Z 0, and it must therefore he concluded that thermodvnamics is inconsistent. ~ i h c ethe argument is completely in the framexorli of the first law, clearly the conservation of energy is an unjustifiable concept. Further investigation as to the point of breakdown is clearly in order, and it is sugs a t e d that Einstein's relation may he the logical starting place.

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