Which of the following changes will cause the free energy of a cell reaction to decrease ?
`Zn|ZnSO_(4)(aq)(x_(1)M)||HCl(aq)(x_(2)M)|H_(2)(g),Pt`.

Options

A. Increase in the volume of `HCl` solution from `100mL` to` 200mL`
B. Increase in the pressure of hydrogen from `1 atm ` to `2 atm`
C. Increase in molarity `x_(2)` from `0.1 ` to `1M`
D. Increase in molarity `x_(1)` from `1M` to `0.1M`.

Answer

c,d

Explanation

`Zn|Zn^(2+)(x_(1)M)||H^(o+))|H_(2)(g),Pt`
Free energy to decrease `implies` cell is more spontaneous `(E_(cell)uarr)`
`Zn+2H^(o+)(x_(2)M) rarr Zn^(2+)(x_(1)M)+H_(2(g))`
`implies E_(cell)=E^(c-)._(cell)-(0.059)/(2) log .([Zn^(2+)]p_(H_(2)))/([H^(o+)]^(2))`
`DeltaG=-ve or E_(cell)=+ve`
`c.` When `x_(2)(0.1M)` changed to `1M`.
`d.` When `x_(1)(1M)` changed to `0.1M`.