Four successive members of the first series of the transition metals are listed below. For which one of them the standard potential value has a positive sign
a) Fe(Z=26) b) Co(Z=27) c) Ni(Z=28) d) Cu(Z=29)
Answer is (D) copper : Z=29
In electrochemical series metals with positive standard potential are placed below hydrogen. Out of the given transition metals, only Cu is placed below hydrogen in the electrochemical series. Therefore, it must have a positive sign for standard potential.