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

Zn_(s) + Ag₂O_(s) + H₂O_(l)→ Zn²⁺ _(aq) + 2Ag_(s) + 2OH^–(aq). Determine Δ_rG⁰ and E⁰ for the reaction.

Given - Zn → Zn^{2 +} + 2e ^- , E⁰ = 0.76V (anode)

Ag₂O + H₂O + 2e ^- →2Ag + 2OH ^- , E⁰ = 0.344V (cathode), n = 2

Δ_rG⁰ = ?

E⁰_cell = ?

Zn is oxidized and Ag₂O is reduced.

Hence, the standard cell potential, E⁰_cell is given as,

E⁰_cell = E⁰_R - E⁰_L

E⁰_cell = 0.344 + 0.76

∴ E⁰_cell = 1.104 V

To calculate the standard Gibb’s free energy, ∆_rG⁰, we use,

∆_rG⁰ = - nE⁰F → Equation 1

= - 2×96487×1.104 J

= - 213043.296 J

∴ ∆_rG⁰ = - 2.13×10⁵ J

The standard cell potential, E⁰_cell is 1.104 V and the standard Gibb’s free energy, ∆_rG⁰ is - 2.13×10⁵ J