Calculate the standard cell potential of galvanic cell in which the following reaction take place :
(Given `E_(OP)^(@)Cr, Cd, Fe^(2+), Ag` are `0.74V, 0.40V, -0.77V` and `-0.80V` respectively)
`(a) 2Cr_((s))+3Cd_((aq.))^(2+) rarr 2Cr_((aq.))^(3+)+3Cd`
(b) `Fe_((aq.))^(2+)+Ag_((aq.))^(+) rarr Fe_((aq.))^(3+)+Ag_((s))`
Calculate the `Delta_(r)G^(@)` and equilibrium constant of the reactions.

Explanation

`E_("cell")^0=E_(OP_(Cr//Cr^(3+)))^0+E_(RP(Cd^(2+)//Cd)^0`
`[2Crto2Cr^(3+)+6e,3Cd^(2+)+6eto3Cd]`
`=0.74+(-0.40)=+0.34V`
Six electrons (n=6) are used in redox change
`-/_\_rG^0nE^0F=6xx0.34xx96500J=196800J`
or `/_\_rG^0=-196.86kJ`
Also `-/_\_rG^0=2.303xx8.314xx298log K`
`K=3.17xx10^(34)`