L31S07_FreeEnergy_EquiK 04-06-07

L31S07_FreeEnergy_EquiK 04-06-07 - Chem 1A, L31:...

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Unformatted text preview: Chem 1A, L31: "Free Energy and K" Effect of P, V, T, n Equilibrium Le Chtelier's Principle A system in equilibrium subjected to a stress will react in a direction that tends to reduce the stress Q=K Q>K Q=K V P Q Previously At 25 C, K ~ 6.8, H = -57.2 kJ mol-1 2 NO2 (g) N2O4 (g) Q= PN2O4 P2NO2 = K at Equilibrium (T) L18-4 A.Pines,M.Kubinec.UCB L18-5 A.Pines,M.Kubinec.UCB Ammonia Synthesis (Haber-Bosch 1910) (HaberN2 (g) + 3 H2 (g) 2 NH3 (g) Multiple Equilibria A H1 K1 B B H2 K2 C = [C] [A] A H3 K3 C H ~ -92 kJ mol-1 Slow at 25o C. High T means low K: Raise P K3 = [C][B] ][B [A][B] ][B = K1 K2 Actual Conditions: T~ 500 oC P~ 200 atm L18-9 H3 = H1 + H2 A.Pines,M.Kubinec.UCB A.Pines,M.Kubinec.UCB A.Pines,M.Kubinec,UCB L31-1 L18-10 ChemQuiz 30.5 Consider the equilibria: Ni(H20)62+ Ni(H20)62+ Ni(NH3)62+ 6 NH3 K1 3 en K3 en en NH3 Ni(NH3)62+ Ni(en)32+ What is the color of K2 ? Ni(en)32+ 1) Blue A.Pines,M.Kubinec,UCB 2) Violet 3) Can't tell Can' L31-2 Free Energy and Equilibrium Free Energy and Temperature G = H -T S lnK = -H 1 S + R R T aA+bB G > 0 Summary G = 0 cC+dD G, K K<1 K=1 G < 0 K>1 G? intercept = H? slope = -S? S? ln K intercept = R slope = R -H? G = RT ln K A.Pines,M.Kubinec,UCB K = exp ( -G) RT T Endo L25-4 A.Pines,M.Kubinec,UCB Endo L33-10 1/T - H 1 S + lnK = R T R G G = H -T S T H S HS HS HS lnK lnK + - - - + + - + 1/T L25-9 A.Pines,M.Kubinec,UCB A.Pines,M.Kubinec,UCB 1 Chem 1A, L31: "Free Energy and K" Free Energy and Equilibrium aA+bB G > 0 Spontaneous cC+dD G = 0 G, K K<1 K=1 G < 0 Spontaneous K>1 G= RT ln K A.Pines,M.Kubinec,UCB K = exp ( -G) RT L31-5 ChemQuiz 31.1 What are G and K for H2O(l) H2O(g) at 25C? 25 1) G< 0 K>1 A.Pines,M.Kubinec,UCB 2) G= 0 K<1 3) G> 0 K<1 L31-6 Free Energy and Temperature G = H - TS S lnK = -H 1 + T R R Exo Endo lnK Endo K Exo 1/T A.Pines,M.Kubinec,UCB T L31-8 A.Pines,M.Kubinec,UCB 2 Chem 1A, L31: "Free Energy and K" Free Energy and Temperature G = H -T S lnK = - H 1 S + R T R G intercept = H slope = -S S ln K intercept = R slope = R -H T Endo A.Pines,M.Kubinec,UCB Endo L31-9 1/T - H 1 S + lnK = LnK and Free G = H -T S Energy R R T G T H S HS HS HS lnK lnK + - - - + + - + 1/T L31-10 A.Pines,M.Kubinec,UCB ChemQuiz 31.2 Shown is a plot of lnK vs 1/T lnK for I2 (s) I2 (g). Which is the corresponding plot for CO2 (s) CO2 (g) ? 1) 2) 3) lnK lnK 1/T A.Pines,M.Kubinec,UCB L31-11 A.Pines,M.Kubinec,UCB 3 Chem 1A, L31: "Free Energy and K" Free Energy and the Reaction Quotient G(Reactants) G = G(P) G(R) G(P) G < 0 G = 0 G > 0 Q<K Q=K Q>K G = G RT lnK = G(Products) G = G+ + RT lnQ 0 lnK A.Pines,M.Kubinec,UCB L31-13 ChemQuiz 31.3 What are G and K at equilibrium at 25C for 25 H2O(l) H2O(g) ? 1) G < 0 K>1 A.Pines,M.Kubinec,UCB 2) G = 0 K<1 3) G > 0 K<1 L31-14 ChemQuiz 31.4 [xi] Which is true at t1? A (aq) + 2 B (aq) (aq) 1) Q > K A.Pines,M.Kubinec,UCB C (aq) (aq) t1 t 2) Q = K 3) Q < K L31-16 A.Pines,M.Kubinec,UCB 4 Chem 1A, L31: "Free Energy and K" Lecture Complete A.Pines,M.Kubinec,UCB L31-18 A.Pines,M.Kubinec,UCB 5 ...
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