Concept:A redox reaction is spontaneous if the metal being oxidized sits "higher" (has a more negative reduction potential) in the electrochemical series than the metal ion being reduced.
Solution:- Zinc (\( Zn \)) has a standard reduction potential of \( -0.76 \text{ V} \).
- Copper (\( Cu \)) has a standard reduction potential of \( +0.34 \text{ V} \).
- Because Zn is a stronger reducing agent than Cu, solid Zinc will naturally oxidize to \( Zn^{2+} \) while forcing \( Cu^{2+} \) to reduce to solid Cu.
- This is the classic, highly spontaneous reaction that powers the Daniell cell (yielding \( +1.10 \text{ V} \)).
Why other options are incorrect:Option B is the electrolysis of molten NaCl, requiring massive external energy. Option C is the reverse of the Daniell cell and is non-spontaneous. Option D is an extremely non-spontaneous decomposition.
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