lectrochemistry: Using Standard Cell Potentials
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Ox amp; Red |
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Half-reactions |
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Voltaic Cells |
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Cell Voltage |
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Calc. Potentials |
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Batteries |
| Electrolytic Cells |
Putting it Together:
While unearthing an ancient village in the Euphrates river valley, you come across the following device shown below. Translating the the Assyrian glyphs on the delicate buttons, you have determined that the instrument is a construction used to calculate cell potentials!
Click
on an upper electrode and a lower electrode to see the reduction equations
for each. Click on "Sum" to see the potential for a cell constructed
with the two electrodes.
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Use the above device to answer the following questions that fascinated and entertained these ancient people for centuries:
Which of the following metals is the better reducing agent at standard
conditions?
Hint: remember that reducing agents are themselves oxidized.
Good
job! The higher positive potential (+ 0.74 V) is generated when chromium
atoms transfer their electrons.
Do
copper atoms have the higher positive potential when they transfer
their electrons? (- 0.34 V)
Do
silver atoms have the higher positive potential when they transfer
their electrons? (- 0.80 V)
Which of the following metal ions is the better oxidizing agent at standard
conditions?
Hint: remember that the more positive the potential, the more product-favored the reaction.
Well
done! Silver ions are much happier accepting electrons (+ 0.80 V)
Do
nickel ions generate the higher potential when they are reduced? (-
0.24 V) Try again...
Actually,
zinc ions are more difficult to reduce (a poorer oxidizing agent)
than the other two ions in this list! (- 0.76 V)
What
is the net cell potential for a voltaic cell constructed of chromium and
silver electrodes? (you will need to calculate this by hand!)
Excellent!
Chromium is oxidized in this cell (+0.74); silver ion is reduced (+0.80)
You've
kept both reactions as reductions! Try again... (hint: Cr(s) is oxidized)
You've
changed both half-reactions to oxidations! Try again... (hint: Ag+
is reduced)
You've
reversed the wrong half-reaction! Try again... (hint: Ag+
is reduced)
Please
enter a value!
Does
this potential indicate a spontaneous reaction? Try again... (hint:
Ag+ is being reduced and Cr metal is being oxidized)
Try
again... (hint: Ag+ is being reduced and Cr metal is being
oxidized)
Using
the figure above, determine the highest possible potential for a voltaic
cell using one electrode from upper set and one from the lower set of
the mechanism:
Great
Job! Zn(s) is the best reducing agent of both the upper and lower
rows! (+0.76 V)
Pd(s)
is easily reduced, but relatively difficult to oxidize; not the best
choice for the anode, where oxidation occurs. Try again...
Please
enter a metal!
Is
the oxidation potential of this metal higher than that of say... Zn?
Well
Done! Pd(s) is the best oxidizing agent of both the upper and lower
rows! (+0.99 V)
Zn(s)
is easily oxidized, but relatively difficult to reduce; not the best
choice for the cathode, where reduction occurs. Try again...
Is
the reduction potential of this metal higher than that of say... Pd?
| Note: as you practice calculating net cell potentials, it will become easier to determine the cathode (oxidation) half-reaction by simple inspection! |
Activate the debriefing to test your understanding of the meaning and use of standard reduction potentials.
Using Standard Cell Potentials 
