In the button cell widely used in watches and other devices, the following reaction takes place: $$\mathrm{Zn(s)+Ag_2O(s)+H_2O(l)\longrightarrow Zn^{2+}(aq)+2Ag(s)+2OH^-(aq)}$$ Determine E° and $\Delta_rG^{\circ}$ for the reaction. (Given $E^{\circ}_{\mathrm{Ag_2O/Ag}} = 0.80$ V, $E^{\circ}_{\mathrm{Zn^{2+}/Zn}} = -0.76$ V)

CBSE Class 12 · 2005 · Delhi · Redox Reactions and ElectrochemistryShort Answer

In the button cell widely used in watches and other devices, the following reaction takes place:

Zn (s) + A g_{2} O (s) + H_{2} O (l) ⟶ Z n^{2 +} (aq) + 2Ag (s) + 2O H^{-} (aq)

Determine E° and

Δ_{r} G^{\circ}

for the reaction.
(Given

E_{A g_{2} O/Ag}^{\circ} = 0.80

E_{Z n^{2 +} /Zn}^{\circ} = - 0.76

Answer: E° = 1.56 V; Δ_rG° ≈ −301 kJ mol⁻¹

Zinc is oxidised (anode), Ag

_{2}

O reduced (cathode),

n = 2

E_{ce l l}^{\circ} = 0.80 - (- 0.76)

E_{ce l l}^{\circ} = 1.56 V

Gibbs energy:

Δ_{r} G^{\circ} = - n F E_{ce l l}^{\circ} = - 2 \times 96500 \times 1.56

Δ_{r} G^{\circ} = - 3.01 \times 1 0^{5} J = - 301 kJ mo l^{- 1}

CBSE Class 12 Board · 2005 · Delhi · Subjective