Question

A half cell is prepared by `K_(2)Cr_(2)O_(7)` in a buffer solution of `pH =1`. Concentration of `K_(2)Cr_(2)O_(7)` is `1M`. To 3 litre of this solution `570 gm` of `SnCI_(2)` is added which is oxidised completely to `SnCI_(4)`.
Given: `E_(Cr_(2)O_(7)^(-2)//Cr^(+3).H^(+))^(@) = 1.33V, (2.303)/(F) RT = 0.06`,
Atomic of mass `Sn = 119, E_(Sn^(+4)//Sn^(+2))^(@) = 0.15`
Half cell potential `E_(Cr_(2)O_(7)^(-2)//Cr^(+3))^(@)` after teh reaction of `SnCI_(2)` is:
A. `1.187`
B. `1.191`
C. `1.285`
D. None of these

Answer 1

Correct Answer - B
`Cr_(2)O_(7)^(-2)+14H^(+)+6e^(-)underset("F mole 2")underset("1 mole 3")(rarr.)2Cr^(+3)+7H_(2)O`
`E=1.33-(0.059)/(6)"log"(2^(2))/(2(10^(-1))^(14))`