The predominance area for ClO₄^- does not extend belw +1.19 V at pH = 0, while that for Eu²⁺ does not extend above -0.5 V.

Since there is no overlap the ions can react.

The electrochemical potential for the reaction is given by:

E⁰ (ox. agent) - E⁰ (red. agent) = E⁰ (rxn) = +1.7 V