Four successive members of the first series of transition metals are listed below. For which one of the of standard potential `(E_(M^(2+)//M)^(@))` value has a positive sign ?

Options

A. `Co = (Z = 27)`
B. `Ni (Z = 28)`
C. `Cu (Z = 29)`
D. `Fe(Z = 26)`

Answer

C

Explanation

Copper does not liberate `H_(2)` gas from acids and thus shows positive of `E^(@) (E^(@)` for `Cu^(2+)//Cu` is `+ 0.34 V`).
For other metals, `E^(@)` is-ve.