Which of the following changes will increase the `EMF` of the cell `:`
`Co(s)|CoCl_(2)(M_(2))||HCl(M_(2))||(H_(2),g)Pt`

Options

A. Increae in the volume of `CoCl_(2)` solution from `100mL` to `200mL`.
B. Increase `M_(2)` from `0.1 M` to `0.50M`.
C. Increase the pressure of the `H_(2)(g)` from `1.0` to `2.0 atm`.
D. Increase `M_(1)` from `0.01M` to `0.50M`.

Answer

b

Explanation

`Co+2H^(o+) rarr Co^(2+)+H_(2)`
`Q=([Co^(2+)])/([H^(o+)]^(2))`
`E=E^(c-)-(0.0591)/(2) log .([Co^(2+)])/([H^(o+)]^(2))`
`E` will increase when `[H^(o+)]` increases of `[Co^(2+)]` decreases.