CONSTRUCTING AND EVALUATING A VOLTAIC CELL
Purpose:
The purpose of this laboratory exercise is to construct and evaluate a voltaic cell.
Discussion:
A voltaic electrochemical cell uses spontaneous oxidation–reduction reactions to create
voltage. The combination of the right anode and cathode will work together to create a positive
cell potential. In this lab, the following half–reactions are available. The standard reduction
potentials are included to help speed the anode/cathode selection process.
Al3+ + 3 e–  Al
E° = –1.662 V
Fe3+ + 3 e–  Fe
E° = –0.037 V
Ag+ + e–  Ag
E° = 0.7996 V
Mg2+ + 2 e–  Mg
E° = –2.372 V
Cd + 2 e  Cd
E° = –0.4030 V
Mn + 2 e  Mn
E° = –1.185 V
Ca2+ + 2 e–  Ca
E° = –2.868 V
Ni2+ + 2 e–  Ni
E° = –0.257 V
Co2+ + 2 e–  Co
E° = –0.28 V
Pb2+ + 2 e–  Pb
E° = –0.1262 V
Cr3+ + 3 e–  Cr
E° = –0.744 V
Zn2+ + 2 e–  Zn
E° = –0.7618 V
2+
–
–
Cu + 2 e  Cu
2+
2+
–
E° = 0.3419 V
A metal anode must be chosen that will spontaneously oxidize to run the cell. An inert
carbon electrode will be used as the cathode. A cation that will spontaneously reduce must be
chosen as the solute in the cathode solution. If the right pair of half–reactions is correctly set up
in an electrochemical cell with 0.1 M solutions of their cations, a voltmeter can be used to verify
the standard cell potential.
Objectives:
In this lab, you will...
1. construct a voltaic cell.
2. evaluate the cell by calculating the percent error between the observed and
theoretical cell potentials.
Materials:
Laptop/LabPro/LoggerPro
Conductivity Probes
Student Cell
2 100 mL volumetric flasks
Metal scoopulas
Distilled water
Carbon electrode (cathode)
Metal/Compound combinations:
Al
Al(NO3)3
Fe
AgNO3
Pb
Cd
Cd(NO3)2
Mg
Ca
Ca(NO3)2
Mn
Co
Co(NO3)2
Ni
Cr
Cr(NO3)3
Zn
Cu
CuSO4
Safety:
 Wear safety goggles at all times.
 Handle all chemicals with extreme care.
Fe(NO3)3
Pb(NO3)2
Mg(NO3)2
Mn(NO3)2
Ni(NO3)2
Zn(NO3)2
Procedure:
1. Choose a metal anode that will spontaneously oxidize and a cation cathode that will
spontaneously reduce. No lab group can use the same combination.
2. Connect a LabPro to a laptop. Connect the conductivity probes to the LabPro. Open
LoggerPro; it should automatically recognize and calibrate the conductivity probes.
3. Create 100.00 mL of 0.1 M solutions for the two compartments. Be careful – many
of these compounds are hydrates, which affects their molar mass.
4. Remove the porous cup from the cell. Pour ~50 mL of the cathode solution into the
plastic cup part of the cell. Pour ~30 mL of the anode solution into the porous cup.
Make sure you keep track of which solution is in which part of the cell!
5. Place the porous cup back into the cell. Clamp the metal anode into to the solution in
the porous cup. Clamp the carbon cathode into the solution in the plastic cup. Move
to step 6 quickly.
6. Immediately attach the two conductivity probes to the two terminals attached to the
electrodes. If the voltage reads a consistent negative value, record the absolute value
of the cell potential.
7. Record the voltage every 10 seconds for three minutes.
Cleanup:



Detach the conductivity probes. Remove the electrodes from the solutions. Clean
them very thoroughly by wiping them down with a paper towel, thoroughly rinsing
them three times with distilled water, and rinsing them lightly once with acetone.
Allow them to dry completely before returning them to their bag.
Pour the contents of the two containers down the drain with plenty of running water.
Rinse them thoroughly three times with tap water and then three times with distilled
water. Finally, rinse them lightly once with acetone. Allow them to dry completely
before returning them to their box. Be sure to wrap the porous cup back up in its
bubble wrap.
Disassemble the apparatus and put the components away properly.
Expectations:
 Data: Tabulate the cell potential data and time.
 Analysis: Draw the cell schematic, the cell diagram, and the balanced equation for
the cell.
 Calculations:
o Show the mathematics involved with determining how to create your 0.1 M
solutions.
o Calculate the average cell potential produced by the voltaic cell over three
minutes.
o Calculate the standard cell potential for the cell. Remember, standard cell
potentials are for 1 M solutions, but we used 0.1 M solutions to ease the
creation of the electrolyte solutions…
o Calculate the absolute and percent errors using the experimental cell
potential of your cell and the standard cell potential of your cell.