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A half-reaction is multiplied by three so the electrons balance. What happens to its standard reduction potential?
AIt is multiplied by three
BIt is divided by three
CIt changes sign only
DIt stays exactly the same
Answer & Solution
Correct answer: D. It stays exactly the same
1. Potential is energy per unit of charge, not a total amount of energy.
2. Scaling a half-reaction multiplies both the energy and the charge by the same factor.
3. A ratio whose top and bottom are scaled equally does not change.
4. So the standard reduction potential is unchanged by any stoichiometric factor.
5. Multiplying the potential by three double counts the scaling and inflates the cell voltage.
6. Dividing by three applies the scaling backwards and shrinks it instead.
7. The sign only flips when a reduction is rewritten as an oxidation, which is a different operation.
_Source: OpenStax Chemistry (CC BY 4.0), Chs 7 and 17, section 17.3 Standard Reduction Potentials_
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