L31-post - Lecture 31 Feel the Power: Energy Sources From...

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1 Lecture 31 Feel the Power: Energy Sources Key Idea: The power we use in our daily lives comes at a cost. 2 Ag + (ag) + Cu (s) 2 Ag (s) + Cu 2+ (ag) 2 e - G o rxn = G f o (Cu 2+ ( aq )) 2 G f o (Ag + ( aq )) = 88.76 kJ/mol Can this Gibbs free energy be converted to work without heat release? From Monday: Direction of the flow of electrons in a galvanic cell Potential, E Electron energy Cu 2+ , Cu Ag + , Ag E cell Voltmeter E cell Cu – 2e Cu 2+ Ag + + e Ag Just like water, electrons flow because of the difference in the potential energy, E Electrons flow from the anode to the cathode Anode (oxidation), higher energy , more negative potential (E o ) Cathode (reduction), lower potential , more positive potential (E o ) G o = nF E o where F = charge on 1 mol of e ’s = 96500 Coulombs/mol, n = # mol of e ’s exchanged, and 1 J = 1 Coulomb x 1 Volt. 2 Ag + (ag) + Cu (s) 2 Ag (s) + Cu 2+ (ag) 2 e - G o rxn = G f o (Cu 2+ ( aq )) 2 G f o (Ag + ( aq )) = 88.73 kJ/mol Therefore: E o cell = −∆ G o rxn / 2 F = 0.46 V and G o = nF E o +0.799 -77.11 +0.339 -65.49 E o (V) G f o (kJ/mol) Cu 2+ + 2e - Cu Ag + + e - Ag half-reaction G o f = n F E o () 0.799 0.339 0.46 oo o cell cathode anode o cell EE E E Ag half cell E Cu half cell EV ∆= −− =−= Zn 2+ + 2e - Zn 147.06 -0.762 For a zinc
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L31-post - Lecture 31 Feel the Power: Energy Sources From...

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