Question
In the button cell 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 ΔrG° and E° for the reaction.
Solution
The formula of standard cell potential is
Eocell = Eo right – Eoleft
Eocell = 0.344 – ( – 0.76)
Eocell = 0.344+0.076 V
Eocell = +1.104 V
In balanced reaction there are 2 electron are transferring so that n = 2
Faraday constant, F = 96500 C mol−1
Eocell = + 1.104 V
Use formula
∆rGθ = – nFEocell
Plug the value we get
Then, = −2 × 96500 C mol−1 × 1.104 V
= −212304 CV mol−1
= −212304J mol−1
= −212.304kJ mol−1
= −213.04 kJ
