Galvanic Cell and Zn Cu Zn Essay

Objective: The purpose of this lab was to combine two metals into a galvanic cell and measure the voltage to determine reduction and oxidation of each metal.
Hypothesis: If we perform our experiment correctly, we should see that our cell potentials should come out to be around the same as the actual cell potentials found in the book.
Data:
Voltage of each half-cell versus the zinc electrode

Voltage
Anode
Cathode
Zn vs. Ag
1.31
Zn
Ag
Zn vs. Cu
0.90
Zn
Cu
Zn vs. Fe
0.43
Zn
Fe
Zn vs. Mg
0.52
Zn
Mg
Zn vs. Pb
0.40
Zn
Pb

Predicted and Measured Cell Potentials
Anode
Cathode
Equation for the Cell Reaction
Predicted Potential from Experimental Data
Measured Potential
Mg
Pb
Mg + Pb2+ → Mg2+ + Pb
0.40 – 0.52 = -0.12 V
- 0.88 V
Cu
Ag
Cu + Ag2+ → Cu2+ + Ag
1.31 – 0.90 = 0.41 V
0.39 V
Fe
Cu
Fe + Cu2+ → Fe2+ + Cu
0.90 – 0.43 = 0.47 V
0.47 V
Fe
Ag
Fe + Ag2+ → Fe2+ + Ag
1.31 – 0.43 = 0.88 V
0.88 V
Pb
Cu
Pb + Cu2+ → Pb2+ + Cu
0.90 – 0.40 = 0.50 V
0.51 V
Mg
Cu
Mg + Cu2+ → Mg2+ + Cu
0.90 – 0.52 = 0.38 V
1.34 V

Part 2 Data Table

Voltage
Anode
Cathode
Zn(s) ׀Zn2+ (1.0 M) ׀׀ Cu2+(0.0010 M) ׀ Cu(s)
0.86
Zn
Cu

Equation for Cell Reaction
Predicted Potential
Measured Potential
Zn + Cu2+ → Zn2+ + Cu
0.8112 V
0.90 V

E = 0.90 V – 0.0592 V log[Zn2+] 2 [Cu2+]

E = 0.90 V – 0.0592 V log[1 M] 2 [0.001 M]

E = 0.90 - 0.0296 ( 3 )

E = 0.8112 V

Part 3 Data Table

Voltage
Anode
Cathode
Zn(s)׀ Zn2+ (1.0 M) ׀׀ Ag+(unknown M) ׀ Ag(s)
0.71
Zn
Ag

Equation for Cell Reaction
Calculated [Ag+]
Calculated Ksp AgCl
Reported Ksp AgCl
Zn + 2Ag+ → Zn2+ + 2Ag

1.8 x 10-10

E = 1.31 V – 0.0592 V log[Zn2+] 2 [Ag+]2

E = 1.31 V – 0.0592 V log[1] 2 [Ag+]2

Calculations
Reduction Equation
Electrode Potential using Zinc as the Standard, Eº Zn
Accepted Electrode Potential using Hydrogen as Standard, Eº
Eº Zn - Eº
Ag+ e- → Ag
1.31 V
0.799 V
1.31 V – 0.799 V =
0.511 V
Cu2+ + 2e- → Cu
0.90 V
0.337 V
0.90 V – 0.337 V =
0.563 V
Fe2+ + 2e- → Fe
0.43 V
-0.440 V
0.43 V – (-0.440) V
=
0.87 V
Mg2+ + 2e- → Mg
0.52 V
-2.37 V
0.52 V – (-2.37) V
=
2.89 V
Pb2+ + 2e- → Pb
0.40 V
-0.126 V
0.40 V – (-0.126) V
=
0.526 V

Questions:
1. An electrode potential is the amount of reduction and oxidation between two metals.
2.
3. The values found using the zinc electrode as a standard should be relatively close to the values based on the standard hydrogen electrode. This was proven to be true for all except for the Magnesium and Lead reaction.
4. The concentrations of the metals and the voltage of the half cell versus the zinc electrode can cause a difference between the experimental and reported values.
5. A negative value for standard potential

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