Question

`Zn^(2+) to Zn_((s)),E^(@)=-0.76V`
`Cu^(2+)toCu_((s)),E^(@)=-0.34V`
which of the following is spontaneous
A. `Zn^(2+)toCutoZn+Cu^(2+)`
B. `Cu^(2+)+ZntoCu+Zn^(2+)`
C. `Zn^(2+)+Cu^(2+)toZn+Cu`
D. none of these

Answer 1

Correct Answer - B
`Zn^(2+)toZn_((s)),E^(o)=-0.76V`
`Cu^(2+)toCu_((s)),E^(o)=-0.34V`
A redox reaction is feasible if `E_(cell)` is positive.
`Zn^(2+)+2e^(-)toZn_((s)),E^(o)=-0.76V`
`underline(Cu^(2+)+2e^(-)toCu_((s)),E^(o)=-0.34V" ")`
`thereforeCu^(2+)+ZntoZn^(2+)+Cu,E_(cell)=E_((Cu^(2+)//Cu))^(o)-E_((Zn^(2+)//Zn))^(o)`
Therefore, `E_(cell)=-0.34-(-0.76)`
`=-0.34+0.76=+0.42V`