Home › AP Intermediate 2nd Year › Chemistry › Electrochemical Series ›  If an external opposing voltage of 1.5 V is applied to a Daniell cell (whose E° = 1.10 V), what happens?
ACell continues normally with Zn dissolving at anode
BElectrons flow from Cu to Zn; Zn is deposited at the zinc electrode and Cu dissolves — the cell is being driven in reverse (electrolysis)
CNo flow of current — the opposing voltage exceeds the cell EMF
DThe cell reverses temperature and freezes
Answer & Solution
Correct answer: B. Electrons flow from Cu to Zn; Zn is deposited at the zinc electrode and Cu dissolves — the cell is being driven in reverse (electrolysis)
When the applied opposing voltage **exceeds** E°cell (here 1.5 V > 1.10 V), the cell is driven in reverse: it becomes an **electrolytic cell** — electrons forced from Cu to Zn, Zn²⁺ reduced to Zn at the zinc electrode, and Cu oxidised at the copper electrode. (Option B is correct only at exactly E_ext = E_cell.)
Related questions
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