The standard reduction potentials (in $V$) of a few metal ion/metal electrodes are given below: $Cr^{3+}/Cr = -0.74$; $Cu^{2+}/Cu = +0.34$; $Pb^{2+}/Pb = -0.13$; $Ag^{+}/Ag = +0.8$. The reducing strength of the metals follows the order:

$Cu^{+} + e^- \to Cu$ ; $E^o = X_1 \ V$
$Cu^{2+} + 2e^- \to Cu$ ; $E^o = X_2 \ V$
Then for $Cu^{2+} + e^- \to Cu^{+}$ ; $E^o$ will be ?

$E^o_{cell}$ for the cell: $Pt_{(s)} | H_{2(g)} | HCOOH_{(aq)} || CH_3COOH_{(aq)} | H_{2(g)} | Pt_{(s)}$ at $25^oC$ is ............ $V$. ($K_a$ of $HCOOH = 2.4 \times 10^{-4}$,$K_a$ of $CH_3COOH = 1.8 \times 10^{-5}$,$\log 2 = 0.3$,$\log 3 = 0.477$,$\frac{2.303RT}{F} = 0.059$ or $0.06$)

What is to be done to determine the potential of any half cell?

The standard reduction potentials for $Cu^{2+}|Cu$ and $Cu^{2+}|Cu^{+}$ are $0.337 \, V$ and $0.153 \, V$ respectively. What is the standard electrode potential for the $Cu^{+}|Cu$ half-cell in $V$?

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)