Question #45010

Consider the standard reduction potentials for Neptunium (\ce{Np}) species in aqueous acidic medium ($pH = 0$) at $298\ \text{K}$: \begin{align*} \ce{Np^{4+}{(aq)} + e^-} &\rightleftharpoons \ce{Np^{3+}{(aq)}} \quad &E^\circ = +0.14\ \text{V} \ \ce{NpO2^{+}{(aq)} + 4H^+{(aq)} + e^-} &\rightleftharpoons \ce{Np^{4+}{(aq)} + 2H2O{(l)}} \quad &E^\circ = +0.74\ \text{V} \ \ce{NpO2^{2+}{(aq)} + e^-} &\rightleftharpoons \ce{NpO2^{+}{(aq)}} \quad &E^\circ = +1.13\ \text{V} \end{align*} Three distinct redox reactions involving pairs of these Neptunium species as reactants can occur. Among them, identify the reaction that is both thermodynamically spontaneous and kinetically the fastest (characterized by the lowest activation energy barrier due to the preservation of the actinyl core and hydration spheres). What is the standard cell potential ($E^\circ_{\text{cell}}$) of this specific reaction?