Christa Schafer clschaf@umich.edu Chemistry 125.339
College of LSA 2018
University of Michigan
Galvanic Cells
Abstract:
The purpose of this lab was to determine the concentration of an unknown copper solution using galvanic cells and the flow of electrons from chemical energy into electrical energy. Our hypothesis was that using the oxidation/reductions reaction in a galvanic cell that occur from the transfer of electrons, we would be able to determine the concentration of an unknown copper solution. In order to do this, Lab 10 was broken up into three sub-labs referred to as Lab 10A, Lab 10B, and Lab 10C, respectively. In Lab 10A, the objective was to determine the reduction potential for iron. This was done by submerging different
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Reduction Half Reaction:
Cu+2 + 2e-→ Cu EO =340 mV
Theoretical Ecell Yield:
340 mV- (-760 mV) = 1.1 V
Actual Ecell Yield:
EO =806 mV
Percent Error:
(806mV-1100mV)/1100mV=26.7% Reaction of Zinc and Iron
Oxidation of Half Reaction
Zn → Zn2+ + 2e- EO =-760 mV
Reduction Half Reaction:
Fe+2 + 2e-→ Fe EO = X
Reduction Potential for Iron with Zinc:
293 mV-760 mV = -467
Percent Error:
(467mV-440)/440mV=6.1% Reaction of Copper and Iron
Oxidation of Half Reaction
Fe → Fe+2 + 2e- EO = X
Reduction Half Reaction:
Cu+2 + 2e-→ Cu EO =340 mV
Reduction Potential for Iron with Zinc:
851 mV – 340mV= 511 mV
Percent Error:
(511mV-440)/440mV=16%
Lab 10B:
Reduction Potential Measurement for Copper Sulfate of Varying Molarity
Substance Multimeter Measurement (mV)
0.001 M Cu+2/Cu and 1.0 M Cu+2/Cu 80
Oxidation Reaction:
(0.001 M) Cu → Cu2+ + 2e –
Reduction Reaction
(1M) Cu+2 + 2e-→ Cu
Percent Error:
(88mV-80mV)/88mV=9.1%
Nernst Equation:
Ecell= EO cell – (.0592/n) x log (Q)
Q = log (.001M/1.0M)= -3
N=2
Theoretical Ecell= 0
Ecell= 88 mV
Lab 10C:
Reduction Potential Measurements of Copper and Zinc
Concentration of CuSO4 Multimeter Measurement (mV) -Log(Concentration)
0.1 590 1
0.01 580 2
0.001 540 3
0.0001 500
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