If `E_((Fe^(2+)|Fe))^(o)=-0.441V and E_((Fe^(3+)|Fe^(2+)))^(o)=0.771V`, then what is emf for following reaction ? `[Fe+2Fe^(3+) to 3Fe^(2+)]`.

Options

A. 1.653
B. 1.212 V
C. 0.111 V
D. 0.330 V

Answer

B

Explanation

`Fe^(2+)+2e^(-) to Fe, " "E_(1)^(o)=-0.414V`
`Fe^(3+)+e^(-) to Fe^(2+)," "E_(2)^(o)=0.771V`
Required reaction : `Fe+2Fe^(3+) to 3Fe^(2+)`
`=(Fe to Fe^(2+)+2e^(-))` . . . (oxidation)
`+(2Fe^(3+)+2e^(-) to 2Fe^(2+))` . . . (reduction)
`E_(cell)^(o)=E_(Cathode)^(o)-E_("Anode")^(o)`
`=0.771-(-0.441)`
`E_(cell)^(o)=1.212V`