L26_Thermo5

L26_Thermo5 - The First Law E = W + Q "You cannot win, you...

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The Second Law 0 > Δ + Δ = Δ sur sys S S S The First Law Q W E + = Δ "You cannot win, you can only break even." Henry Bent "You can't break even." Henry Bent
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Second Law of Thermodynamics In any spontaneous process the entropy of the universe must increase Universe= system + surroundings 0 > Δ + Δ = Δ sur sys S S S System 0 > Δ Δ = Δ + Δ = Δ sur rxn sur sys T H S S S S
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12345 5% 26% 2% 65% 2% 1. Δ H > 0 2. Δ S sys > 0 3. Δ S sys = - Δ S sur 4. All of the above 5. None of the above. Consider the process whereby 1.00 mol of H 2 O( s ) is melted to H 2 O(l) at the normal melting point of ice, 273.15 K. Which of the following is true for this process?
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In which case MUST a reaction be spontaneous, independent of T? 1. DH > 0; DSsys = 0 2. DH = 0; DSsys < 0 3 . DH < 0; DSsys > 0 4 DH > 0; DS s y 5 . No n e o f th a b ov 2% 5% 19% 71% 1. Δ H > 0; Δ S sys = 0 2. Δ H = 0; Δ S sys < 0 3. Δ H < 0; Δ S sys > 0 4. Δ H > 0; Δ S sys > 0 5. None of the above
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Δ S sys = Δ S rxn Δ S sur =- Δ H/T Δ S univ Spontaneous? + + (exo) + yes - - (endo) - no + - (endo) ? yes if | Δ S sys |>| Δ S sur | -+ ( e x o ) ? yes if | Δ S sys |<| Δ S sur | 0 > Δ Δ = Δ + Δ = Δ sur rxn sur sys T H S S S S Very exothermic rxns: Δ H driven, Δ S is not very important Biological rxns: Δ H ~ 0 entropy and temperature are very important
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In general, can calculate Δ S rxn
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This note was uploaded on 07/22/2008 for the course CHEM 115b taught by Professor Reisler during the Spring '08 term at USC.

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L26_Thermo5 - The First Law E = W + Q "You cannot win, you...

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