of 2):
Use two tall 150-mL beakers to construct each half-cell. Note that each of the following half
cells are constructed from an electrode (often the metal involved in the reaction) immersed in a
solution containing the reacting ion. Choose among the following (step 2) half-cell couples and
connect them with a salt bridge which is made of an absorbent paper soaked in NH
4
NO
3
or KCl
solution (0.1 M conc. Will work). Use a digital voltmeter set your meter to the most sensitive
DCV scale, and measure the positive voltage for each cell. If voltages are in the mV unit (for
example if you did get a value at the 2000m scale, it would read in mV unit) convert the
value to volts and record them. Draw a diagram of each cell in your lab notebook and show the
way voltmeter wires, called leads (pronounced as leeds), are connected to your cell to read a
positive voltage. Specifically, indicate which leads (+ or ) are connected to which electrodes.
Black lead wire is connected to the meters negative terminal (ground or Com.) and the red lead
wire is connected to the meters positive terminal using each wires banana jack connector.
The alligator clip end of each wire should be clipped to the top part of each electrode.

Step 1. Construct these numbered half cells by pouring 40 mL of each liquid in a tall 200-mL
beaker.
1) Pb / 0.10 M Pb(NO
3
)
2

2) Zn / 0.10 M ZnSO
4

3) Cu / 0.10 M CuSO
4

4) Cu / equal volumes of 6.0 M NH
3
and 0.10 M CuSO
4
(20 mL + 20 mL)
5) Graphite rod / equal volumes of saturated bromine water and 0.10 M KBr (20/20 mL)
Note: Place this half-cell under the fume hood since bromine vapors are toxic! Avoid
inhalation of the vapors!

Step 2. Combine the following numbered half cells with a fresh salt bridge each time. Connect
the meter to each cell and observe and record the potential trend. Wait for 2-3 minutes in each
case (or until readings stabilize) and record the potential (volts) for each cell.
Voltaic Cell
Half cells (numbers correspond to the above numbered half-cells)
A.
1 and 2
B.
1 and 3
C.
2 and 3 (Room Temperature)
D.
2 and 3 (Cooled in ice/water mixture)*
E.
1 and 5
F.
3 and 5
G.
2 and 4
H.
3 and 4
Procedure to cool down Voltaic couple D: Place each tall beaker in a larger beaker containing
ice/water mixture. Allow 10 minutes to equilibrate the cold temperature. Stir each solution after
5 minutes. Next, record the temperature of each tall beakers contents. Record the room
temperature. Chem 1B
Instructor: Kamran Golestaneh
Revised : 12/01/05 Page 2 of 5

Step 3. Go to the electrolytic cell set-up in the lab. This cell is a glass U-tube that will be
connected to a power supply using two graphite electrodes.
Note: Never plug-in or unplug electrical cords with wet hands. Be sure no water or solution is
ever in contact with electrical equipment such as a power supply.
1) Be sure that the power supply is off and unplugged.
2) Remove the graphite rods from the alligator clips and rinsing them with pure water.
Connect them to the alligator clips again.
3) Empty the contents of the U-tube in a labeled waste container. Rinse the U-tube with
water and mount on the ring stand.
4) Pour 40 mL of 0.1 M KI solution in a clean 50-mL beaker and add 3 drops of the
phenolphthalein indicator and mix with a stirring rod.
5) Pour the mixture into the U-tube and insert the graphite rods, one in each end of the U-
tube.
6) Be sure that the voltage dial on the power supply is set to zero (counter-clockwise)
7) Plug-in the meter into the 110VAC power outlet and turn the power switch on.
8) Connect your digital voltmeter to the graphite electrodes.
9) Next connect the power supply leads to the graphite electrodes. Be sure that the positive
(+) lead is connected to the electrode with the positive voltmeter lead and the negative (-)
lead is connected to the electrode with the negative voltmeter lead.
Note: At this point check and be sure that the metal connectors of the graphite rods are not
touching each other or the current will not pass through the cell!
10) Observe the cell and Slowly increase the voltage dial to power the cell to the minimum
voltage at which you start to see tiny bubbles of gas at one or both electrodes. Record (in
Volts) the cell potential.
11) Record your detailed observation on chemical products forming on the electrodes and any
colors forming.

Draw a diagram of this electrolytic cell in your notebook. This cell is made up of two graphite
electrodes (cathode/anode) immersed in a solution of 0.1 M KI. Be sure to indicate the polarity
(+ or -) of each electrode lead in your notebook.


Refer to the next page for the report summary sheets. Chem 1B
Instructor: Kamran Golestaneh
Revised : 12/01/05 Page 3 of 5


Report Calculations and Results Summary Sheets:

The purpose of this experiment:
To understand and apply important electrochemical concepts and calculations involved in voltaic
and electrolytic cells. These calculations include the relationships between cell potential,
concentration and temperature (Nernst equation) as well as free energy and equilibrium constant
calculations.

Refer to your Chem1B report guidelines to prepare your report. For this report, you do not need
to include a conclusion page in your report.

Review the fundamental concepts of electrochemistry in your textbook and lecture notes. Review
concepts dealing with calculation of overall standard-state cell potentials, Concentration cells
and Nernst equation for calculation of cell potentials at non-standard-state conditions
(Temperature and concentrations).

1) Calculate the expected cell potential for each cell including the electrolytic cell involving the
power supply. Remember to consider the non-standard temperature factor in your calculation.
Use the general form of the Nernst equation (see your textbook for details) and include the actual
cell temperature in your calculations:


E
cell
= E
ocell
R.T/(n.F) ln Q


G = -n.F.E
cell


You also need the equilibrium constant/free energy relationship.



Chem 1B
Instructor: Kamran Golestaneh
Revised : 12/01/05 Page 4 of 5

Part I.
Summary of Results (Show detailed sample calculations for Cell A, the copper concentration
cell and the Electrolytic cell in the Calculations sections of your report).

Table 1 Measured and calculated cell potentials (E), Volts

Cell
half cells
Measured E Temp. (Deg C) Expected E
% Error
A
1 and 2




B
1 and 3




C
2 and 3




D (cooled)
2 and 3




E
1 and 5




F
3 and 5




G
2 and 4




H
3 and 4




Electrolytic KI
solution



Note: Concentrations are listed in the experimental procedures.

Part II. Show the cell diagram (notation) for cells:
Cell
half cells

Cell diagram (notation)
A
1 and 2

G
3 and 4

Electrolytic KI
solution


Part III. Calculate the free energy change G (based on E
cell
) for the following cells under the
initial experimental conditions. Also, calculate the equilibrium constant, K for each cell under
the standard cell conditions.
Cell
half cells
G


K

A
1 and 2


C
2 and 3


F
3 and 5


Electrolytic KI
solution


Part IV. Complete the following cell diagram components using the cell sketches and write your
findings in the tables on the next page. (Note: Left cell must be the anode). Chem 1B
Instructor: Kamran Golestaneh
Revised : 12/01/05 Page 5 of 5



Half cells


1 and 2 1 and 5
2 and 4

Sign of voltmeter polarity at A



Electrode material B



Electrode material C



Reacting specie in solution at D



Reacting specie in solution at E



Direction of electron flow at F



Balanced half reaction at D



Balanced half reaction at E







A
F
voltmeter
D E
C
B


C
Power supply
A
F
B


Electrode material at C
Sign of power supply polarity at A
Direction of electron flow at F
Note: Enter or for electron
flow direction.
Anode must be the left electrode
Half-cell reaction
(balanced) at electrode B:
Half-cell reaction
(balanced) at electrode C: