The standard emf of the cell, `Cd(s) |CdCI_(2) (aq) (0.1M)||AgCI(s)|Ag(s)` in which the cell reaction is `Cd(s) +2AgCI(s) rarr 2Ag(s) +Cd^(2+) (aq)` is `0.6915 V` at `0^(@)C` and `0.6753V` at `25^(@)C`. The `DeltaH` of the reaction at `25^(@)C` is,-

Options

A. `-176kJ`
B. `-234.7kJ`
C. `+123.5kJ`
D. `-167.26kJ`

Answer

D

Explanation

`(dE)/(dT)=((0.6753-0.6915))/((25-0))=-6.48xx10^(-4)Vdeg^(-1)`
`triangleH_(298)=-neF+nFT(dE)/(dT)=-2xx0.6753xx96500+2xx96500xx298xx(-6.48xx10^(-4))`
`=2xx96500(-0.6753-0.1931)=-167.6KJ`