The standard reduction potential data at `25^(@)C` is given below
`E^(@) (Fe^(3+), Fe^(2+)) = +0.77V`,
`E^(@) (Fe^(2+), Fe) = -0.44V`,
`E^(@) (Cu^(2+),Cu) = +0.34V`,
`E^(@)(Cu^(+),Cu) = +0.52 V`,
`E^(@) (O_(2)(g) +4H^(+) +4e^(-) rarr 2H_(2)O] = +1.23V`
`E^(@) [(O_(2)(g) +2H_(2)O +4e^(-) rarr 4OH^(-))] = +0.40V`,
`E^(@) (Cr^(3+), Cr) =- 0.74V`,
`E^(@) (Cr^(2+),Cr) = - 0.91V`,
Match `E^(@)` of the redox pair in List-I with the values given in List-II and select the correct answer using the code given below teh lists:
`{:(List-I,List-II),((P)E^(@)(Fe^(3+),Fe),(1)-0.18V),((Q)E^(@)(4H_(2)O hArr 4H^(+)+4OH^(+)),(2)-0.4V),((R)E^(@)(Cu^(2+)+Curarr2Cu^(+)),(3)-0.04V),((S)E^(@)(Cr^(3+),Cr^(2+)),(4)-0.83V):}`
Codes:

Options

A. `{:(,,P,Q,R,S),(,A,4,1,2,3):}`
B. `{:(,,P,Q,R,S),(,B,2,3,4,1):}`
C. `{:(,,P,Q,R,S),(,C,1,2,3,4):}`
D. `{:(,,P,Q,R,S),(,D,3,4,1,2):}`

Answer

D

Explanation

`triangleG_(Fe^(3+)//Fe)^(@)=triangleG_(Fe^(3+)//Fe^(2+))^(@)+triangleG_(Fe^(2+)//Fe)^(@)`
`rArr -3 xx FE_((Fe^(+3)//Fe))^(@)=-1 xx FE_((Fe^(+3)//Fe^(+2))^(@)+(-2 xx FE_((Fe^(+2)//Fe))^(@))`
`rArr E_(Fe^(+3)//Fe)^@=-0.04V`
(Q) `O_(2) (g)+2H_(2)O+4e^(-) to 4OH" "E^(@)=0.40 .......(i)`
`2H_(2)O to O_(2)(g)+4H^(+)+4e^(-) " "E^(@)=-1.23V .........(ii)`
`So, 4H_(2)O Leftrightarrow 4H^(+)+4OH.........(iii)`
`E^(@)" for "III"rd reduction =0.40-1.23=-0.83V"`
(R) `triangleG_((Cu^(+2)//Cu))^(@)=triangleG_((Cu^(+2)//Cu^(+))^(@)+triangleG_((Cu^(+)//Cu))^(@)`
`-2 xx FE_(Cu^(+2)//Cu)^(@)=-1 xx FE_(Cu^(+2)//Cu^(+))^(@)+(-1 xx F x E_(Cu^(+)//Cu))^(@)`
`rArr E_(Cu^(+2)//Cu)^(@)=-0.18V,`
(S) `triangleG_(Ci^(+3)//Cr^(+2))^(@)=triangleG_(Cr^(+3)//Cr)^(@)+triangleG_(Cr//Cr^(+2))^(@)`
`-1 xx F xx E_(Cr^(+2)//Cr^(+2))^(@)=-3 xx F xx E_(Cr^(+3)//Cr)^(@) +(-2 xx F xx E_(Cr//Cr^(+2))^(@)`
`rArr E_(Cr^(+3)//Cr^(+2))^(@)=-0.4V`