In conjunction with a standard hydrogen electrode, the La3+|La half-cell is the anode and the standard cell potential is 2.52V. What is the standard reduction potential for the La3+|La half-cell?

Answer 1

If the La3+/La electrode is the anode, that means the reaction at that electrode is
La ==> La^+3 + 3e (remember that oxidations occurs at the anode) and the cell potential is +2.52 v. So the standard reduction reaction is La^+3 + 3e ==> La and the potential is -2.52 v.