L38S09_RedoxCellPot+04-27-09

L38S09_RedoxCellPot+04-27-09 - Chem 1A L 38"Reduction...

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Unformatted text preview: Chem 1A, L 38: "Reduction Potentials" Summary ©A.Pines,M.Kubinec,UCB L38-1 Amino Acid pKa’s +N 2.0 O 10 O C C C 3.9 O 9.2 N N C C C C pH = 7.0 C O - Aspartic Acid O O + C N N C C C N N 6.0 C C ©A.Pines,M.Kubinec,UCB 1.8 O O Histidine L38-2 ChemQuiz© 37.2 pKa= 9.0 What is the total effective charge on the amino acid cysteine at pH 5.0 ? N + C O C C S pKa= 8.0 pKa= 2.2 Cysteine A) + 1 ©A.Pines,M.Kubinec,UCB B) 0 C) -1 L38-3 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" Summary ©A.Pines,M.Kubinec,UCB L38-5 LEO goes GER ©A.Pines,M.Kubinec,UCB L38-6 Loss of Electrons is Oxidation goes Gain of Electrons is Reduction ©A.Pines,M.Kubinec,UCB L38-7 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" Redox and Electrochemistry Cu2+ (aq) + Zn (s) aq) (s) oxidizer ? Zn2+ (aq) + Cu (s) aq) (s) Zn2+ (aq) + Cu (s) aq) (s) oxidizer reducer ? Cu2+ (aq) + Zn (s) aq) (s) reducer Spontaneous: ∆G˚ < 0, K > 1 Zn Zn Zn2+ + 2 eCu2+ + 2 eReduction Cu L38-8 Oxidation ©A.Pines,M.Kubinec,UCB OIL RIG ©A.Pines,M.Kubinec,UCB L38-9 Oxidation Reduction Is Is Loss Gain of electrons ©A.Pines,M.Kubinec,UCB L38-10 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" Standard Galvanic Cell Anode - e- ∆Єº Salt Bridge e- + Cathode 1.0 M Oxidation Zn Zn2+ + 2 e- Zn2+ Cu2+ 1.0 M Cu Reduction Cu2+ + 2 e- Notation: Zn Zn2+ (1.0 M) Cu2+ (1.0 M) Cu (1.0 (1.0 ∆Єº = 1.10 V ©A.Pines,M.Kubinec,UCB L38-11 Red Cat Reduction is Cathode L38-12 ©A.Pines,M.Kubinec,UCB Standard Reduction Potentials Cu2+ + 2 e2 H+ + 2 eZn2+ + 2 eZn Cu H2 Zn Єº = +0.34 V Єº = +0.00 V Єº = -0.76 V Reducer Oxidizer Oxidizer ©A.Pines,M.Kubinec,UCB L38-13 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" Standard Reduction Potentials º º ∆Єº = ЄCu – ЄZn = Є º(right) – Є º(left) H2 (g) 1.00 atm Pt SHE: 2 H+ + 2 e+ H+ Єº (V) H2 (g) 0.00 - Pt H2 H Cu2+ Cu + +0.34 Cu 1.0 M + Pt H2 H+ Zn2+ Zn - -0.76 L38-14 + ©A.Pines,M.Kubinec,UCB ChemQuiz© 38.1 What forms when Cu is placed in H2SO4? H2SO4 1.0 M A) Cu2+ ©A.Pines,M.Kubinec,UCB B) H2 C) nothing L38-15 ChemQuiz© 38.2 What forms when Zn is placed in H2SO4? H2SO4 1.0 M A) Zn2+ ©A.Pines,M.Kubinec,UCB B) H2 C)nothing C)nothing L38-17 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" ChemQuiz© 38.3 Which of the following will oxidize H2? H2 (g) Pt 1.00 atm Which of the following will be reduced by H2? A) Cu2+ ©A.Pines,M.Kubinec,UCB H+ 1.0 M B) Cu C)Zn2+ C)Zn L38-19 ChemQuiz© 38.4 When current is allowed to flow, the darker blue solution will become Cu2+ 0.1 M Cu2+ 1.0 M Cu Cu2+ (0.1M) Cu2+ (1.0M) Cu (1.0M) (0.1M) A) Bluer ©A.Pines,M.Kubinec,UCB B) Same C)Lighter C)Lighter L38-21 ChemQuiz© 38.5 ∆Єº (standard) for the cell is Cu2+ 1.0 M Cu2+ 1.0 M Cu Cu2+ (1.0M) Cu2+ (1.0M) Cu (1.0M) (1.0M) A) < 0 ©A.Pines,M.Kubinec,UCB B) = 0 C)> 0 C)> L38-23 ©A.Pines,M.Kubinec,UCB Chem 1A, L 38: "Reduction Potentials" Lecture Complete ©A.Pines,M.Kubinec,UCB L38-25 ©A.Pines,M.Kubinec,UCB ...
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