The $EMF$ of the cell $Ni | Ni^{2+} (1.0 \ M) || Au^{3+} (1.0 \ M) | Au$ is ............ $V$. (Given: $E^o_{Ni^{2+}/Ni} = -0.25 \ V$; $E^o_{Au^{3+}/Au} = 1.50 \ V$)

The standard electrode potentials $(E^{0}_{Red})$ of four elements $A, B, C,$ and $D$ are $-3.05 \ V, -1.66 \ V, -0.40 \ V,$ and $0.80 \ V$ respectively. Which of the following is the most reactive?

Iron displaces copper from its salt solution,because

Standard electrode potentials are given:
$A^{+}/A = -2.93 \ V$ $B^{+}/B = 0.80 \ V$
$C^{2+}/C = -2.37 \ V$ $D^{3+}/D = -0.74 \ V$
Increasing order of reducing power of these metals:

At ${25 \, ^\circ C}$,the standard reduction potentials for $Li^+/Li$,$Ba^{2+}/Ba$,$Na^+/Na$,and $Mg^{2+}/Mg$ are $-3.05 \, V$,$-2.73 \, V$,$-2.71 \, V$,and $-2.36 \, V$ respectively. Which of the following is the strongest oxidizing agent?

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