What happens to the Gibbs free energy in a spontaneous electrochemical process?

Reduction potential of ions are given below:

$ClO_4^{-}$	$E^{\circ} = 1.19 \ V$
$IO_4^{-}$	$E^{\circ} = 1.65 \ V$
$BrO_4^{-}$	$E^{\circ} = 1.74 \ V$

The correct order of their oxidising power is:

In a cell,the following reactions take place:
$Fe^{2+} \rightarrow Fe^{3+} + e^{-}$ $\quad$ $E^{\circ}_{Fe^{3+} / Fe^{2+}} = 0.77 \, V$
$2I^{-} \rightarrow I_{2} + 2e^{-}$ $\quad$ $E^{\circ}_{I_{2} / I^{-}} = 0.54 \, V$
The standard electrode potential for the spontaneous reaction in the cell is $x \times 10^{-2} \, V$ at $298 \, K$. The value of $x$ is .... (Nearest Integer)

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

The standard reduction potential for $Li^{+}/Li$,$Zn^{2+}/Zn$,$H^{+}/H_2$ and $Ag^{+}/Ag$ is $-3.05$,$-0.762$,$0.00$ and $+0.80 \ V$. Which of the following has the highest reducing capacity?

$A$ standard hydrogen electrode has zero electrode potential because