Chem208_Lecture_21_BW

Chem208_Lecture_21_BW - course of a spontaneous change. or...

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1 Today: Thermodynamics (Chapter 19) Exam coverage: Chapters 15–18, 24 PS9 will go out in lecture on Thursday Exam II: Tonight, 7:30-9:00 Room Assignments are shown on last Tuesday’s handout
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2 Spontaneous Changes A spontaneous change is a change that, once begun, has a tendency to occur without being driven by an external influence. A spontaneous change does not necessarily occur rapidly.
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3 Thermodynamics What determines whether a process will proceed spontaneously? H 2 O ( l ) H 2 0 ( s ) or H 2 O ( s ) H 2 0 ( l ) 2 H 2 ( g ) + O 2 ( g ) 2 H 2 0 ( i ) or 2 H 2 O ( l ) 2 H 2 ( g ) + O 2 ( g )
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4 Natural Pattern • Energy and matter tend to become more disordered (or random) • The quantitative measure of this disorder or randomness is known as Entropy
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5 Second Law of Thermodynamics The entropy of the universe increases in the
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Unformatted text preview: course of a spontaneous change. or The entropy of an isolated system increases in the course of a spontaneous change. Isolated System: no interactions with surroundings 6 Statistical View of Entropy Boltzmann: S = k ln W k: Boltzmann constant; k = 1.38 x 10-23 J/K (R = N A k) W: # of microstates of the same energy available to the system 7 ∆ S = q rev /T or dS = dq rev /T = C p dT/T ∆ S = C p ln (T f /T i ) 8 Third Law of Thermodynamics The entropy of a pure, perfect crystal at 0 K is zero. Standard Entropy, S°, is the absolute entropy of a substance in its standard state. 9 Calculate ∆ S° for the oxidation of NH 3 ( g ) by O 2 ( g ) to produce NO ( g ) and H 2 O ( l )...
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This note was uploaded on 03/29/2009 for the course CHEM 2080 taught by Professor Davis,f during the Spring '07 term at Cornell.

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Chem208_Lecture_21_BW - course of a spontaneous change. or...

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