For the reaction:
`2AgCl(s) + H_(2)(g) (1 atm) to 2Ag (s) + 2H^(+) (0.1 M) + 2Cl^(-) (0.1 M), DeltaG^(@) =-43600 J` at `25^(@)` C
Calculate the emf of the cell.
`[log 10^(-n) =-n]`
(b) Define fuel cell and write its two advantages.

Explanation

(a) `DeltaG^(@) =-nFE_("cell")^(@)`
`=-43600 J =-2 xx 96487 C mol^(-1) xx E_("cell")^(@)`
or `E_("cell")^(@) =(-43600)/(-2 xx 96487) = 0.2259 V`
`E_("cell") =E_("cell")^(@) - 0.059/2 log ([0.1]^(2) [0.1]^(2))/1 =0.2259 -0.059/2 log [0.1]^(4)` `=0.2259 + 0.118 = 0.3439 V`
(b) Galvanic cells that are designed to convert the energy of combustion of fuels like hydrogen, methane, methanol etc., directly into electrical energy are called fuel cells. Advantages :
1. Fuel cells produce electricity with an efficiency of about 70% compared to thermal plants whose efficiency is about 40%.
2. Fuel cells are pollution free