L32_Elec4

L32_Elec4 - The Nernst Equation: Summary DG=DG0 + RT ln(Q),...

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The Nernst Equation: Summary D G= D G 0 + RT ln(Q), where Q is rxn quotient D G=w=-qE=-nFE ) ln( 0 Q nF RT E E At equilibrium: D G=0 and Q=K 0 ) ln( E K nF RT For a spontaneous process (galvanic cell): D G<0 E>0 w<0 (system performs electrical work)
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Example: “Pacemaker cells” in heart muscle create voltage pulses, which depend on K + cyclic concentration gradients across cell membrane http://en.wikipedia.org/wiki/Image:ECG_Principle_fast.gif http://en.wikipedia.org/wiki/Cardiac_pacemaker Heart contractions are controlled by electrical pulses due to electrochemistry and permeability of cell membranes to Na + , K + , and Ca 2+ . The concentrations are different in and out of the cells; For K + , [K + ] in = 135 mM; [K + ] out = 4 mM. For Na + , [Na + ] in = 10 mM; [Na + ] out = 145 mM. 0 6.15log(135/4) 94 E E mV   For K + at 37 C:
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A cell is set up with lead and copper electrodes in contact with CuSO 4 (aq) and Pb(NO 3 ) 2 . Standard reduction potentials are: Pb 2+ + 2e = Pb, E 0 =-0.13 V Cu 2+ + 2e = Cu, E 0 =0.34 V. If the sulfuric acid is added to Pb(NO 3 ) 2 forming PbSO 4 precipitate, the cell potential: Increases. Decreases. Not enough informatio. .. 43% 2% 55% 1. Increases. 2. Decreases. 3. Not enough information to answer.
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A cell is set up with lead and copper electrodes in contact with CuSO 4 (aq) and Pb(NO 3 ) 2 . Standard reduction potentials are: Pb 2+ + 2e = Pb, E 0 =-0.13 V Cu 2+
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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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L32_Elec4 - The Nernst Equation: Summary DG=DG0 + RT ln(Q),...

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