Galvanic Cell Emf

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For a Daniell cell built from zinc and copper electrodes with E° values -0.76 V and +0.34 V, what is the standard cell potential?

RankGuru · Accepted Answer

The standard cell potential of a galvanic cell is calculated as E°_cell = E°_cathode - E°_anode, where both values are standard reduction potentials. In a Daniell cell, zinc is oxidised at the anode and copper is reduced at the cathode because copper has the higher (more positive) reduction potential. Substituting, E°_cell = E°_(Cu^2+/Cu) - E°_(Zn^2+/Zn) = (+0.34) - (-0.76) = +1.10 V. The positive sign confirms the cell reaction is spontaneous, which is expected for a working galvanic cell. Option +0.42 V results from incorrectly adding only the magnitudes after a sign error. Option -1.10 V reverses anode and cathode, which would describe a non-spontaneous electrolytic process. Option +0.34 V mistakenly reports only the cathode value. This is the canonical Daniell cell calculation in NCERT electrochemistry. Plausibility check: a positive E°_cell corresponds to a negative Gibbs free energy through ΔG° = -nFE°_cell, confirming spontaneity of the zinc-copper reaction.

Galvanic Cell Emf

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