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Chemistry Honors – Voltaic Cell Lab
Electrochemical cells (also called galvanic cells, voltaic cells, or just plain-old batteries) consist of a
system of two metals undergoing redox reactions.
Remember that redox reactions involve gaining and losing electrons. If you just allow the
electrons being lost by one metal to travel through an external wire, before being gained by the other
metal, then those traveling electrons can be used to power an electrical device – a cell phone, mp3
player, etc.
The device below shows a voltmeter, reading 1.10 V, hooked up to the external wire. A typical AA
battery has a voltage of 1.5 V, so this electrochemical cell below could almost power an electrical
device requiring a AA battery. Just replace the voltmeter with that device, and it would work!
The beakers contain solutions of that
metal’s ion.
In this arrangement, the oxidation and reduction half-reactions are carried out in separate vessels. The
two half-cells are connected externally by wire attached to the two electrodes. In order to have a
complete circuit, ions must be free to flow from one half-cell to the other.
Electrons flow between the two reaction beakers via the external wire. The salt bridge is there, to
allow the ions from the solutions to travel between the beakers. This ion flow must occur, so that the
circuit (flow of charge) is complete. REMEMBER! Electrons flow through the wire and ions flow
through the salt bridge. The complete system is an electrochemical cell.
In this experiment you will observe voltages of electrochemical cells using Zinc, Silver, Copper, and
Hydrogen electrodes.
Electrochemistry is an excellent example of how chemistry is applied to everyday life!
What would your world be like without batteries? Batteries are electrochemical cells!
Oxidation: a process in which a substance loses one or more electrons
Reduction: a process in which a substance gains one or more electrons
Anode: an electrode at which oxidation occurs
Cathode: an electrode at which reduction occurs
Procedure:
Go to the following website:
Capitalization matters!!
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/electroChem/
voltaicCell20.html
Part I – H2 | Cu cell – Determining the voltage of a Copper/Hydrogen cell.
1. Choose Copper as the metal, and Cu(NO3)2 as the solution, in the left-side beaker. Note
that the red wire is attached to the copper electrode.
2. Choose Hydrogen electrode as the metal, and HCl as the solution, in the right-side beaker.
Note that the black wire is attached to the hydrogen electrode.
3. Click the power switch on the voltmeter, to start the experiment.
4. Complete the data table below.
Copper
Describe the electron flow…to and
from which metal?
Mark the species that loses
electrons.
Write the oxidation half-rxn under the
species that is undergoing oxidation.
Mark the species that gains
electrons.
Write the reduction half-rxn under the
species that is undergoing reduction.
Mark the element that is the anode.
Mark the element that is the cathode.
Voltage
Hydrogen
Part II – Determining the voltages of other cells.
1. Choose Silver as the metal, and AgNO3 as the solution, in the left-side beaker. Note that
the red wire is attached to the silver electrode.
2. Choose Copper electrode as the metal, and Cu(NO3)2 as the solution, in the right-side
beaker. Note that the black wire is attached to the copper electrode.
3. Click the power switch on the voltmeter, to start the experiment.
4. Record the voltage on the voltmeter, and the direction of electron flow.
5. Repeat Steps 1-4, using a Zinc and Zn(NO3)2 combination on one side, and a Copper and
Cu(NO3)2 combination on another.
voltage is produced.
Choose the sides, so that a positive
This is done with trial and error.
Silver
Copper
Describe the electron flow…to and
from which metal?
Mark the species that loses
electrons.
Write the oxidation half-rxn under the
species that is undergoing oxidation.
Mark the species that gains
electrons.
Write the reduction half-rxn under the
species that is undergoing reduction.
Mark the element that is the anode.
Mark the element that is the cathode.
Voltage
Zinc
Describe the electron flow…to and
from which metal?
Mark the species that loses
electrons.
Write the oxidation half-rxn under the
species that is undergoing oxidation.
Mark the species that gains
electrons.
Write the reduction half-rxn under the
species that is undergoing reduction.
Mark the element that is the anode.
Mark the element that is the cathode.
Voltage
Copper
Voltaic Cells Lab Analysis
Name: __________________________________
1. Look back at the data for the 3 voltaic cells you created.
Each cell involved 1 oxidation and 1 reduction.
Can the table of metal reactivities be used to predict
which substance will be oxidized and reduced in each cell?
Explain below.
2. If a cell is constructed of silver and nickel, predict which substance would be oxidized and reduced.
Diagram this cell below.
a. Label the metals.
b. Label the ions in the solutions.
(assume nitrate solutions, and
nickel(II) ions.
c. Label the cathode and anode.
d. Diagram the flow of ions
through the salt bridge.
e. Diagram the flow of electrons
through the external wire.
f. Write half reactions below
each cell – you will need
coefficients so that # of
electrons in each half-rxn are
equal.