Consider the cell reaction `:`
`Mg(s)+Cu^(2+)(aq) rarr Cu(s) +Mg^(2+)(aq)`
If `E^(c-)._(Mg^(2+)|Mg(s))` and `E^(c-)._(Cu^(2+)|Cu(s))` are `-2.37` and `0.34V`, respectively. `E^(c-)._(cell)` is

Options

A. `-2.71V`
B. `2.71V`
C. `-2.03V`
D. `2.03V`

Answer

B

Explanation

Cell reaction is
`Mg(s)+Cu^(2)+(aq)rarrCu(s)+Mg^(2+)(aq)`
Half reaction at LHE , i.e., oxidation
`MghArrMg^(2+)+2e^(-)`
Half reaction at LHE, i.e., Reduction
`Cu^(2+)(aq)+2e^(-)hArrCu(s)`
Now, `E_(LHE)^(@)=E_(Mg^(2+//Mg))^(@)=-237V`
`E_(RHE)^(@)=E_(Cu^(2+)//Cu)^(@)=+0.34V`
`therefore E_( "cell")^(@)=E_(RHE)^(@)-E_(LHE)^(@)`
`=0.34-(-2.37)=2.71V`