Standard reduction potential of half-cells are given as follows :
`Zn^(2+)+2e^(-) to Zn,E^(o)=-0.76V`
`Fe^(2+)+2e^(-) to Fe,E^(o)=-0.44V`
What is the emf of following reactions ?
`Zn_((S))+Fe_((aq))^(2+) to Zn_((aq))^(+2)+Fe_((S))`.

Options

A. `-1.20V`
B. `+1.20V`
C. `+0.32V`
D. `-0.32V`

Answer

C

Explanation

`E_(cell)^(o)=E_("Reduction (cathode)")^(o)-E_("Reduction (anode)")^(o)`
`=E_(Fe^(2+)|Fe)^(o)-E_(Zn^(2+)|Zn)^(o)`
`=-0.44-(-0.76)`
`+0.32V`