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A cell pairs a gold half-cell at plus 1.498 V with a nickel half-cell at minus 0.257 V. What is the standard cell potential?
A1.755 V
B1.241 V
C2.012 V
D1.498 V
Answer & Solution
Correct answer: A. 1.755 V
1. A galvanic cell always runs in the direction that gives a positive potential.
2. The half-reaction with the more negative potential becomes the anode, so nickel is oxidized.
3. Gold has the higher potential and becomes the cathode.
4. The cell potential is cathode minus anode, so 1.498 volts minus minus 0.257 volts.
5. Subtracting a negative adds, giving 1.498 plus 0.257, which is 1.755 volts.
6. 1.241 volts comes from adding the negative instead of subtracting it.
7. 2.012 volts comes from scaling gold by its three electrons, which the potential never allows.
8. 1.498 volts ignores the nickel half-cell altogether.
_Source: OpenStax Chemistry (CC BY 4.0), Chs 7 and 17, section 17.3 Standard Reduction Potentials_
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