Normal aluminimum electrode cupled with normal hydrogen electrode gives an emf of ` 1.66 V`. So the standard electrode potential of aluminimu is ,

Options

A. ` -1. 66 V`
B. ` + 1.66 V`
C. ` - 0. 83 V`
D. ` + 0. 83 V`

Answer

A

Explanation

Al is above hydrogen in the electrochemical secies, therefore `Al^(3+)` has lesser reuction tendecy as compared with `H^(+)`. Hence, hydrogen electrode acts as anode when copled with aluminum electrode.
` E_("cell")^@=E_(H+//H_2)^@ -D_(Al^(3+)//Al)^@`
` :. 1.66V=0.0V- E_(Al^(3+)//Al)^@`
` E_(Al^(3+)//Al) =- 1.66 V`.