Which of the following metals will not release $H_{2(g)}$ upon reaction with an acid?

$E^o$ values for the half-cell reactions are given below:
$Cu^{2+} + e^- \to Cu^{+} \quad E^o = 0.15 \ V$
$Cu^{2+} + 2e^- \to Cu \quad E^o = 0.34 \ V$
What will be the $E^o$ for the half-cell reaction:
$Cu^{+} + e^- \to Cu$ ? $\dots \ V$

Consider the systems having liquid-solid interface,$(A)$ copper wire in silver nitrate solution and $(B)$ silver wire in copper sulphate solution. Predict which interface will show spontaneous reaction,if $E_{Cu^{2+}/Cu}^{\circ} = 0.34 \ V$ and $E_{Ag^{+}/Ag}^{\circ} = 0.80 \ V$?

The $E^{\circ}$ of $Ce^{4+} / Ce^{3+} = 1.6 \ V$ and $Fe^{3+} / Fe^{2+} = 0.77 \ V$. The $E^{\circ}$ of the reaction where $Fe^{3+}$ oxidises $Ce^{3+}$ is:

$E^o_{cell}$ 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 $0.06$)

Given
$E^o_{\frac{1}{2}Cl_2/Cl^-} = 1.36 \ V$,$E^o_{Cr^{3+}/Cr} = -0.74 \ V$
$E^o_{Cr_2O_7^{2-}/Cr^{3+}} = 1.33 \ V$,$E^o_{MnO_4^-/Mn^{2+}} = 1.51 \ V$
The correct order of reducing power of the species $(Cr, Cr^{3+}, Mn^{2+}, Cl^-)$ will be: