eletrochem - Electrochemical Cells Determination of...

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Electrochemical Cells: Determination of Reduction Potentials for a Series of Metal/Metal Ion Systems, Verification of Nernst Equation Connie Jamieson 12/1/2011 Chemistry 212 section 205 Instructor: Tiffany Ha Lab Partner: Andrew Cedeno Calculations:
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Cu (s) | Cu 2+ (aq) || Ag + (aq) | Ag (s) The half reactions: Cu (s) → Cu 2+ (aq) + 2e - oxidation (black) E° = -0.339 Ag + (aq) + e - → Ag (s) reduction (red) E° = 0.7993V Cu (s) + 2Ag + (aq) ↔ Cu 2+ (aq) + 2Ag (s) cell = +0.463 Concentration: silver 0.1M, copper 0.1M Cell potential at 25°C = 298.15K E cell = E° cell - = +0.463V – Concentration: silver 0.1M, copper 0.01M E cell = E° cell - = +0.463V – Concentration: silver 0.1M, copper 0.001M E cell = E° cell - = +0.463V –
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Zn (s) | Zn 2+ (aq) || Ag + (aq) | Ag (s) The half reactions: Ag + (aq) + e - → Ag (s) reduction (red) E° = 0.7993V Zn (s) → Zn 2+ (aq) + 2e - oxidation (black) E° = +0.762V Zn (s) + 2Ag + (aq) ↔ Zn 2+ (aq) + 2Ag (s) cell = +1.56V Concentration: silver 0.1M and zinc 0.1M Cell potential at 25°C = 298.15K E cell = E° cell - = +1.56V – Part A Cathode (red) Reduction Anode (black) Oxidation E cell (V) Experimental E cell (V) Nernst cell (V) Standard Percent error E cell (V) Experimenta l vs. E cell (V) Nernst Percent error E cell (V) Experimental vs. E° cell (V) Standard a. Ag Cu 0.430V 0.433V 0.463V 0.693% 7.13% b. Ag Zn 1.49V 1.53V 1.56V 2.61% 4.49% Table 1: Determination of Reduction Potentials Half Cell Reaction E red (V) Experimental E red (V) Table value Percent error Ag + + e - ↔ Ag +0.7993V na Cu 2+ + 2e - ↔ Cu 0.369V +0.339V 8.85%
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Zn 2+ + 2e - ↔ Zn -0.691V -0.762V 9.36% Table 2: Calculated Standard Reduction Potentials [Cu|Cu 2+ ] E cell (V) Experimental Log([Cu 2+ ]/[Ag + ] 2 ) 0.1M 0.430V 1 0.01M 0.456V 0 0.001M 0.490V -1 Table 3: Part B: Measured Electrochemical Potentials of Varying [Cu|Cu 2+ ] Solutions Figure Conclusion: This lab consisted of two parts: Part A: to construct electrochemical cells, this was already done, refer to figure 1, and to measure the cell potentials. Part B: verify the Nernst equation; this was done by measuring the cell potential of varying [Cu|Cu 2+ ] solutions. Electrochemical cells are made up of two half-cells, linked by a salt bridge this allows transport of ions in both directions. The purpose of the salt bridge is the cell cannot operate unless the channel is complete. If the half-cell does not stay neutral, the resulting charge difference would stop the cell operation. To avoid this two half-cells are connected by a salt bridge, which acts as a
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This note was uploaded on 02/02/2012 for the course CHEMISTRY 212 taught by Professor Ha during the Spring '11 term at George Mason.

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eletrochem - Electrochemical Cells Determination of...

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