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. Increase the volume of `CoCl_(2)` 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

a,b

Explanation

Cell reaction `:` `Co(s)+2H^(o+)(M_(2))rarrCo^(2+)(M_(1))+H_(2)(g)`
`E_(cell)=E^(c-)._(cell)_-(0.059)/(2)log.([Co^(2+)])/([H^(o+)])(p_(H_(2))-=Q_(cell))`
`a.` Increase in the volume `(i.e.,` dilution `)` of `CoCl_(2)` solution `(i.e.,` decrease in `[Co^(2+)])` will cause `Q_(cell)` to decrease causing `E_(cell)` to increase.
`b.` Increaseing `M_(2)` will cause a reduction in `Q` thus increasing `E_(cell)`
`c.` Increasing `p_(H_(2))` will increase `Q` thus reducing `E_(cell)`.
`d.` Increasing `M_(1)` will increase `Q` thus reducting `E_(cell)`.