Home › AP Intermediate 2nd Year › Chemistry › Electrochemistry ›  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
For an electrochemical cell operating spontaneously, ΔG° is related to E°_cell byWhich of the following statements about electrode potentials is INCORRECT?The overall cell reaction of the lead storage battery on discharge isThe primary cell that cannot be reused after its EMF drops to zero is exemplified byRusting of iron requires which two chemicals in contact with the metal?Fuel cells directly convertThe specific conductivity of a 0.1 M KCl solution is 1.29 × 10⁻² S/cm. The molar conductivMolar conductivity of a strong electrolyte at concentration c is related to its limiting v