Four alkali metals $A$,$B$,$C$ and $D$ have standard electrode potentials of $-3.05 \ V$,$-1.66 \ V$,$-0.40 \ V$ and $0.80 \ V$ respectively. Which one will be the most reactive?

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:

How would you determine the standard electrode potential of the system $Mg^{2+} | Mg$?

What is $emf$?

The cell potential of the given cell is $0.34 \, V$. Write the cell reaction and calculate $E^o_{Cu^{2+}|Cu}$.
$Pt_{(s)} \mid H_{2(g)} (1 \, bar) \mid H^+_{(1 \, M)} \parallel Cu^{2+}_{(1 \, M)} \mid Cu_{(s)}$

Which of the following reactions will be spontaneous in an electrochemical cell constructed from the given standard electrode potentials: $E_{Cl_2 \mid 2Cl^-}^0 = 1.36 \ V$ and $E_{Br_2 \mid 2Br^-}^0 = 1.09 \ V$?