In the button cells widely used in watches and other devices the following reaction takesplace

Q6:In the button cells widely used in watches and other devices the following reaction takesplace:

Zn(s) + Ag₂O(s) + H2O(l) → Zn²⁺⁽aq) + 2Ag(s) + 2OH⁻(aq)

Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction

Solution:

The formula of standard cell potential is

E^o_cell = E^o _right  – E^o_left

Use this link to get all values

http://ncerthelp.blogspot.com/2013/04/the–standard–electrode–potentials–at.html

E^o_cell = 0.344 – ( – 0.76)

E^o_cell = 0.344+0.076 V

E^o_cell = +1.104 V

In balanced reaction there are 2 electron are transferring so that n = 2

Faraday constant, F = 96500 C mol⁻¹

E^o_cell = + 1.104 V

Use formula

∆_rG^θ = – nFE^o_cell

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