50. For a standard Ag-Zn button cell, the net spontaneous reaction is . If the standard Gibbs free e — Electrochemistry Chemistry Question
Question
50. For a standard Ag-Zn button cell, the net spontaneous reaction is $Zn(s) + Ag_2O(s) \rightarrow ZnO(s) + 2Ag(s)$. If the standard Gibbs free energies of formation ($\Delta G_f^\circ$) for $Ag_2O$ and $ZnO$ are -11.2 kJ/mol and -318.3 kJ/mol respectively, what is the $E^\circ_{cell}$?
Answer: A
💡 Solution & Explanation
$\Delta G^\circ_{rxn} = \Delta G^\circ_f(ZnO) - \Delta G^\circ_f(Ag_2O) = -318.3 - (-11.2) = -307.1 kJ/mol = -307100 J/mol$. The reaction transfers 2e- ($Zn \rightarrow Zn^{2+}$). $-nFE^\circ = \Delta G^\circ \implies -2 \times 96500 \times E^\circ = -307100 \implies E^\circ = 307100 / 193000 \approx 1.59 V$.
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