Write Nernst equation and calculate e.m.f. of the cell at 298 k.
`Mg(s)|Mg^(2+)(0.001 M)||Cu^(2+)(0.0001M)|Cu(s)`

Explanation

`Mg//Mg^(2+) (0.001M)//CU^(2+) (0.001M)//Cu`
At anode, `Mg rarr Mg^(2+) + 2e^(-)`
At cathode,
`ul(Cu^(2+) + 2e^(-) rarr Cu)`
`ul(Mg+ Cu^(2+) rarr Mg^(2+) +Cu)`
According to Nernst, `E= E^(@)- (0.059)/(2) "log" ([Mg^(2+)])/([Cu^(2+)])`
`E^(@)= 0.34 + 2.37 = 2.71V`
`E= 2.71- (0.059)/(2) "log" ([0.001])/([0.0001])`
`E= 2.71 - (0.059)/(2) log 10`
`=2.71- 0.0295`
= 2.68V