`FeCr_(2)O_(4)+Na_(2)CO_(3)+O_(2) to Fe_(2)O_(3)darr+Na_(2)CrO_(4)`

Explanation

`E_("oxidant/reductant")=`
`("Mass of oxidant or reductant")/("No. of .e. lost or gained by one mole of oxidant or reductant")`
(a) `2I^(-) to I_(2)^(0)+2e^(-), E_(KI)=(M)/(I)=(166)/(1)=166`
`6e^(-)+Cr_(2)^(6+) to 2Cr^(3+)`
`E_(K_(2)Cr_(2)O_(7))=M/6=(294)/(6)=49`
(b) `2S_(2)^(2+) to S_(4)^((5//2)+)+2e^(-)`
`E_(Na_(2)S_(2)O_(7))=M/1=(158)/(1)=158`
`2e+I_(2)^(0) to 2I^(-)`
`E_(I_(2))=M/2=(254)/(2)=127`
(c) `10e+2N^(5+) to N_(2)^(0)`
`E_(NO_(3)^(-))=("Ionicm. mass")/(5)=(62)/(5)=12.4`
(d) `2Fe^(2+) to Fe_(2)^(3+) +2e^(-)`
`E_(FeSO_(4))=(M)/(1)=(152)/(1)=152`
`6e^(-)+Cl^(5+) to Cl^(-)`
`E_(KClO_(3))=M/6=(122.5)/(6)=20.42`
(e) `2Fe_(3)^((8//3)+) to 3Fe_(2)^(3+)+2e^(-)`
`E_(Fe_(3)O_(4))=M/1=(232)/(1)=232`
`3e^(-)+Mn^(7+) to Mn^(4+)`
`E_(KMnO_(4))=m/3=(158)/(3)=52.67`
(f) `6e^(-)+N_(2)^(0) to 2N^(3-)`
`E_(N_(2))=("M. mass of N"_(2))/(6)=(28)/(6)=4.67`
(g) `FeC_(2)O_(4) to Fe^(3+) +CO_(2)`
`Fe^(2+) to Fe^(3+) +e^(-)`
`C_(2)^(3+) to 2C^(4+) +2e`
`FeC_(2)O_(4) to Fe^(3+) +2C^(4+) +3e^(-)`
`E_(FeC_(2)O_(4))=M/3=(144)/(3)=48`
(h) `S^(4+) to S^(6+)+2e^(-)`
`E_(Na_(2)SO_(3))=M/2=(126)/(2)=63`
`3e^(-)+Cr^(6+) to Cr^(3+)`
`E_(Na_(2)CrO_(4))=M/3=(162)/(3)=54`