L28S07_FreeEnergy1 03-23-07

L28S07_FreeEnergy1 03-23-07 - Chem 1A Lecture 28"Free...

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Unformatted text preview: Chem 1A Lecture 28: "Free Energy; Direction of Change" Spontaneous Process The Reverse Never Occurs Summary warm hot A.Pines,M.Kubinec,UC Pressure Equilibration Temperature Equilibration E = 0 w = 0 q = 0 S = kB ln W warm cool S = S > 0 qrev T L29-4 Isothermal Expansion/Compression Pext = F/A Adiabatic Expansion/Compression Pext = F/A Const T : E = H = 0 q + ww 0 =- = hhExpansion w<0 q>0 S > 0 Compression w>0 q<0 S < 0 L20-6 q = 0 : E = w hhExpansion w<0 q=0 S > 0 2000 University of California Compression w>0 q=0 S > 0 2000 University of California A.Pines,M.Kubinec,UCB L28-1 L20-7 ChemQuiz 27.4 An ideal gas is isothermally compressed. What is Ssurr ? h- 1) < 0 A.Pines,M.Kubinec,UCB 2) = 0 3) > 0 L28-2 Thermodynamic Parameters Summary kJ/mol J/K mol kJ/mol Hf S Gf Hf S C(s) Mg(s) kJ/mol J/K mol Gf kJ/mol H2(g) O2(g) 0 0 131 205 0 0 0 0 6 33 0 0 569 CO2(g) 394 214 394 H2O(g) 242 189 229 H2O(l) 286 70 257 A.Pines,M.Kubinec,UCB MgO(s) 602 27 MgO(s) C2H2(g) 227 CH3CH2OH(l) 278 201 209 161 175 L24-5 G = H -TS H > 0 Endothermic H > 0 Endothermic H S Free Energy and Reactions H S G <0 <0 Exothermic More order No T Low T High T All T H S K (s) + H20 (l) K+ (aq) + OH- (aq) + H2 (g) aq) aq) C2H5OH (l) + 3 O2 (g) - + - 2 CO2 (g) + 3 H20 (l) AlBr3 (s) + - + + + + - - + L24-8 S > 0 Less order S > 0 Less order Al (s) + 3/2 Br2 (l) 2 MgO (s) + C (s) 2 Mg (s) + CO2 (s) L24-7 A.Pines,M.Kubinec,UCB A.Pines,M.Kubinec,UCB A.Pines,M.Kubinec,UCB 1 Chem 1A Lecture 28: "Free Energy; Direction of Change" Phase Transition (Order Hvap H2 O Hvap Tbp vap liq Disorder) qrev T Vaporization of a liquid at Tbp S = 40 kJ 100 C A.Pines,M.Kubinec,UCB Tbp Hvap S = Tbp Svap ~ 90 J/K mol (H2O ~ 110 J/K mol) L28-5 ChemQuiz 28.1 At the Triple Point of water, H O L ice, liquid and vapor are all in ice, equilibrium. Which transition P S G involves the greatest increase Temperature in entropy? 2 Tc 1) S L A.Pines,M.Kubinec,UCB 2) L G 3) G S L28-6 Triple Point of Water H2O (g) H2O (l) H2O (s) Equilibrium = universe is indifferent liquid S H H S A.Pines,M.Kubinec,UCB L28-8 A.Pines,M.Kubinec,UCB 2 Chem 1A Lecture 28: "Free Energy; Direction of Change" Tracking the Entropy of the Universe H2O (l) H2O (g) Ssurr + Ssys = Suniv 0 Hvap + Ssys = Suniv T G univ Hsys T Ssys= -T S0 0 A.Pines,M.Kubinec,UCB L28-9 Gibbs Free Energy G = H - TS G = H -TS Spontaneous Process H S G G < O G = Gf(Products) Gf(Reactants) A.Pines,M.Kubinec,UCB L28-10 Free Energy Space G = H -TS H > 0 Endothermic H > 0 Endothermic H S <0 <0 Exothermic More order No T Low T High T All T H S S > 0 Less order S > 0 Less order A.Pines,M.Kubinec,UCB L28-11 A.Pines,M.Kubinec,UCB 3 Chem 1A Lecture 28: "Free Energy; Direction of Change" ChemQuiz 28.2 The reaction shown is spontaneous at 25 C. H for the reaction is: 2 NO2 (g) N2O4 (g) 1) < 0 A.Pines,M.Kubinec,UCB 2) = 0 3) > 0 L28-12 ChemQuiz 28.3 Which is the correct plot of G vs. T for the reaction H2O (l) H2O (g)? 1) G T H 2O L S G Temperature Tc P 2) G 3) T G T A.Pines,M.Kubinec,UCB L28-14 Thermodynamic Parameters kJ/mol J/K mol kJ/mol Hf S Gf Hf S C(s) Mg(s) kJ/mol J/K mol Gf kJ/mol H2(g) O2(g) 0 0 131 205 0 0 0 0 6 33 0 0 569 CO2(g) 394 214 394 H2O(g) 242 189 229 H2O(l) 286 70 257 A.Pines,M.Kubinec,UCB MgO(s) 602 29 MgO(s) C2H2(g) 229 CH3CH2OH(l) 298 201 209 161 175 L28-16 A.Pines,M.Kubinec,UCB 4 Chem 1A Lecture 28: "Free Energy; Direction of Change" Free Energy and Reactions H S G K (s) + H20 (l) H2O(l) + O2(g) AlBr3 (s) K+ (aq) + OH- (aq) + H2 (g) aq) aq) H2O2(l) - + - + - + + + + + - - L28-17 Al (s) + 3/2 Br2 (l) 2 MgO (s) + C (s) 2 Mg (s) + CO2 (s) A.Pines,M.Kubinec,UCB ChemQuiz 28.4 CO2 (g) + CaO (s) CaCO3 (s) H ~ -200 KJ mol-1 S~ -200 J mol-1K-1 For the reaction: For what temperature range is the reaction spontaneous? spontaneous? 1) < 1000 A.Pines,M.Kubinec,UCB 2) ~ 1000 3) > 1000 L28-18 Lecture Complete A.Pines,M.Kubinec,UCB L28-20 A.Pines,M.Kubinec,UCB 5 ...
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This note was uploaded on 08/19/2009 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at Berkeley.

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