The standard reduction potentials of two half cells `Al^(3+) (aq) | Al`and `Mg^(2+)(aq) | Mg` are -1.66V and -2.36V respectively. Calculate the standard cell potential. Write the cell reactions also.

Answer

`0.70V,3Mg+2Al^(3+)to3Mg^(2+)+2Al`

Explanation

E.M.F. can be positive only if oxidation takes place at Mg-electrode, i.e., the cell reaction is:
`3mg+2Al^(3+)to3Mg^(2+)+Al`
`E_(cell)^(@)=E_(Al^(3+)//Al)^(@)-E_(Mg^(2+)//Mg)^(@)=-1.66-(-2.36)V=0.70V`.