Conductivity (Unit Siemen's 'S') is directly proportional to area of the vessel and the concentration of the solution in it and is inversely proportionals to the length of the vessel, then the unit of constant of proportionality is :

Options

A. `S m mol^(-1)`
B. `S m^2 mol^(-1)`
C. `S^(-2) m^2 mol`
D. `S^2 m^2 mol^(-2)`

Explanation

(A) `MnO_4^-` will oxidise `Cl^-` ion according to equation
`Mn^(7+)+5e rarr Mn^(2+)`, `2Cl^(- ) rarr Cl_2+2e`,
Thus `E_(cell)^0=E_(OPCl^-//Cl_2)^0+E_(RPMn^(7+)//Mn^(2+))^0`
=-1.40+1.51 =0.11V
or reaction Is feasible
`MnO_4^(-)+ 5e rarrMn^(2+)` , `Fe^(3+) rarr Fe^(2+)+e`,
`E_(cell)^0=E_(OPCl^-//Cl_2)^0+E_(RPMn^(7+)//Mn^(2+))^0`
-0.77+1.151 = 0.74V
or reaction is feasible
Thus `MnO_4^-` will not oxidize only `Fe^(2+)` and `Fe^(3+)` in aqueous HCl but it will also axidise `Cl^(-)` to `Cl_2`. Suitable oxidant should not oxodise `Cl^(-)` to `Cl_2` and should oxidise only `Fe^(2+)` and `Fe^(3+)` in redox titration.