5_60_lecture12

5_60_lecture12 - MIT OpenCourseWare http:/ocw.mit.edu 5.60...

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MIT OpenCourseWare http://ocw.mit.edu 5.60 Thermodynamics & Kinetics Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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5.60 Spring 2008 Lecture #12 page 1 Criteria for Spontaneous Change The 2 nd Law gave the Clausius inequality for spontaneous change dS > đ q/T surr. The 1 st law gave us dU = đ q + đ w Putting the two together, assuming only pV work, gives us the following general criterion for spontaneous change: ** dU + p ext dV – T surr dS < 0 ** Equilibrium is when there is no possible change of state that would satisfy this inequality. We can now use the general criterion above under specific conditions Consider first an isolated system (q=w=0, Δ V=0, Δ U=0) Since dU=0 and dV=0, from the general criterion above, then (dS) U,V > 0 is the criterion for spontaneity for an isolated system And equilibrium for an isolated system is then achieved when entropy is maximized. At maximum entropy, no spontaneous changes can occur.
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This note was uploaded on 07/31/2011 for the course CHM 170 taught by Professor Lemtayo during the Spring '11 term at MIT.

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5_60_lecture12 - MIT OpenCourseWare http:/ocw.mit.edu 5.60...

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