The standard hydrogen electrode has a zero electrode potential because .....

The standard reduction potentials at $25^o C$ are given below. Which is the strongest reducing agent?
$Zn^{2+}_{(aq)} + 2e^{-} \rightleftharpoons Zn_{(s)}$,$E^o_{RP} = -0.762 \, V$
$Cr^{3+}_{(aq)} + 3e^{-} \rightleftharpoons Cr_{(s)}$,$E^o_{RP} = -0.740 \, V$
$2H^{+}_{(aq)} + 2e^{-} \rightleftharpoons H_{2(g)}$,$E^o_{RP} = 0.00 \, V$
$Fe^{3+}_{(aq)} + e^{-} \rightleftharpoons Fe^{2+}_{(aq)}$,$E^o_{RP} = 0.77 \, V$

The standard electrode potential (in $V$) values for $Al^{3+}/Al$ and $Tl^{3+}/Tl$ are respectively:

Can the absolute electrode potential of an electrode be measured?

Given $E_{Fe^{+3}/Fe}^{\circ} = -0.036 \ V$ and $E_{Fe^{+2}/Fe}^{\circ} = -0.439 \ V$,calculate the standard electrode potential for the reaction: $Fe^{+3}_{(aq)} + e^{-} \rightarrow Fe^{+2}_{(aq)}$ (in $V$)

Electrode potentials of five elements $A, B, C, D$ and $E$ are respectively $-1.36 \ V, -0.32 \ V, 0 \ V, -1.26 \ V$ and $-0.42 \ V$. The reactivity order of these elements is: