Download Voltaic Cells Web Activity

Voltaic Cells Web Activity
Name____________________________________ Period _______
What are the electrical properties of chemical reactions?
Go to http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/electroChem/voltaicCell20.html .
Also the activity can be accessed by clicking the link on Mr. Belland’s AP Chemistry website. Your screen should
look like the figure.
This simulation contains an apparatus for measuring the voltage generated by chemical reactions. This apparatus
is called a voltaic cell. Pop out menus will allow you to select metals (electrodes) and ionic solutions to be placed
into two beakers that are connected by a salt bridge. You can then connect the metals to a voltmeter to measure
the cell voltage (E°).
Click on the left pop -out tab for metals and select silver. Click on the left pop-out tab for solutions and select
AgNO3 (aq). Use the right tabs and select Cu and Cu(NO3)2 (aq). Click on the power switch of the voltage meter.
Observe the action of the simulation. Use the following drawing to draw arrows showing the direction of
movement of the electrons and the voltage shown on the voltmeter.
1
1.
What is the voltage (E°) generated by the chemical reaction?
2.
What direction are the electrons flowing?
3.
What happens to the electrons that are on the Ag metal electrode?
4.
What happens to the electrons that are on the Cu metal electrode?
5.
Write a net ionic equation representing what is happening in the left beaker. (This is called a half reaction.)
6.
Write a net ionic equation representing what is happening in the right beaker. (This is called a half reaction.)
7.
Combine the two half reactions into a complete reaction.
8.
Determine what happens if you reverse the cell by placing the Ag/AgNO3 in the right beaker and the Cu/Cu(NO3)2
system in the left beaker. Explain what you observe.
Repeat the procedure above for all the combinations in the following table, and:
 Record the cell voltages shown on the voltmeter for each condition.
 Record the direction of electron flow from electrode (metal) to electrode(metal)
Experiment #
Left Cell
Right Cell
Voltage (E°)
Direction of Electrons
1
Ag/AgNO3 Cu/Cu(NO3)2
From
to
2
Ag/AgNO3
Zn/Zn(NO3)2
From
to
Cu/Cu(NO3)2 Zn/Zn(NO3)2
From
to
3
4
Ag/AgNO3
H2/HCl
From
to
5
Cu/Cu(NO3)2
H2/HCl
From
to
6
Zn/Zn(NO3)2
H2/HCl
From
to
2
For each of the six combinations in the table above write the two half reactions that are combined to generate the overall
reaction. Write the half reaction equations to accurately represent which half reaction gains electrons (called reduction)
and which loses electrons (called oxidation) and label the oxidation and reduction half reactions. The reactions for the
Ag/AgNO3 and Cu/Cu(NO3)2 is shown as an example.
Experiment 1:
Cu → Cu2+(aq) + 2eAg+(aq) + 1e- → Ag
Oxidation
Reduction
Experiment 2:
Experiment 3:
Experiment 4:
Experiment 5:
Experiment 6:
Assume that the H2/HCl half reaction is assigned a voltage of 0.0 V. This means that the voltage of the other three half
reactions can be assigned relative to it. Use the information from the previous chart to assign a voltage to each of the
half reactions below.
Silver: Ag+ + e- → Ag
Voltage =
Copper: Cu2+ + 2e- → Cu Voltage =
Zinc: Zn2+ + 2e- → Zn
Voltage =
3