Which of the following has been universally accepted as a reference electrode at all temperatures and has been assigned a value of zero volt?

The standard electrode potential $({E^o})$ for $OCl^{-} / Cl^{-}$ and $Cl^{-} / \frac{1}{2}Cl_2$ respectively are $0.94 \ V$ and $-1.36 \ V$. The ${E^o}$ value for $OCl^{-} / \frac{1}{2}Cl_2$ will be ............... $V$.

What is the standard reduction potential $(E^o)$ for $Fe^{3+} \to Fe$ ? ............... $V$
Given that :
$Fe^{2+} + 2e^- \to Fe;$ $E^o_{Fe^{2+}/Fe} = -0.47 \ V$
$Fe^{3+} + e^- \to Fe^{2+};$ $E^o_{Fe^{3+}/Fe^{2+}} = +0.77 \ V$

If the standard potential of the electrochemical cell for the reaction $2Ag_{(aq)}^+ + Cd_{(s)} \to Cd_{(aq)}^{2+} + 2Ag_{(s)}$ is $1.20 \ V$,calculate the standard Gibbs free energy change in $kJ$.

Electrode potentials $(E^o)$ are given below:
$Cu^{+}/Cu = +0.52 \ V$
$Fe^{3+}/Fe^{2+} = +0.77 \ V$
$\frac{1}{2} I_{2(s)}/I^{-} = +0.54 \ V$
$Ag^{+}/Ag = +0.88 \ V$
Based on the above potentials,the strongest oxidizing agent will be:

For the given cell reaction $Fe^{2+}_{(aq)} + Ag^{+}_{(aq)} \rightarrow Fe^{3+}_{(aq)} + Ag_{(s)}$,the standard cell potential is:
Given:
$Ag^{+} + e^{-} \rightarrow Ag \quad E^0 = x \ V$
$Fe^{2+} + 2e^{-} \rightarrow Fe \quad E^0 = y \ V$
$Fe^{3+} + 3e^{-} \rightarrow Fe \quad E^0 = z \ V$