How to Calculate Galvanic Cell Potentials (Ecell)
We must first consider the standard reduction potentials for each half-reaction:
➞ E°cell
➞ values are listed in Table 17-1 of my *Chemistry Video Notes,* and also below...
Table 17-1 = Standard Reduction Potentials (in Volts) at 25°C (298K) for Many Common Half-Reactions.
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ex: Why is the voltage 1.10 V in the redox reaction occurring in the galvanic cell below?
The overall balanced redox equation is:
Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)
Anode - where oxidation occurs:
Zn → Zn2+ + 2e- ; E°Zn = + 0.76 V (from Table 17-1)
Cathode - where reduction occurs:
Cu2+ + 2e- → Cu ; E°Cu2+ = + 0.34 V (from Table 17-1)
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So, overall we have:
E°cell = E°Zn + E°Cu2+
NOTE: If the half-reaction is reversed in Table 17-1, you must change the sign (+/-) of E°, but if the half-reaction is multiplied through by an integer, the value of E° doesn't change!!
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Cell Potential Calculations (Ecell)
ex: Calculate the overall cell potential of the following reaction:
Cu(s) + 2Fe3+(aq) → Cu2+(aq) + 2Fe2+(aq)
➞ break up into half-reactions...
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Line Notation
When describing a galvanic cell (electrochemical cell), line notation is used.
➞ the anode compartment is listed on the LEFT.
➞ the cathode compartment is listed on the RIGHT.
ex: A few sample problems back, we had an example with zinc and copper:
Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)
Here it is again, in an easy-to-follow handwritten format...
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In my next post on SECTION 17 - Electrochemistry, my 3rd article on this subject,
We'll do more galvanic cell examples and practice balancing half-reactions and calculating E°cell.
Be sure to check it out!...