What is the standard electrode potential $(E^o)$ for the electrode represented by $Pt, O_2(1 \, atm) | 2H^+(1 \, M)$?

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 potential at $298 \ K$ for the following half-cell reactions is given as:
$Zn^{2+}_{(aq)} + 2e^{-} \rightarrow Zn_{(s)} ; \quad E^{\circ} = -0.762 \ V$
$Cr^{3+}_{(aq)} + 3e^{-} \rightarrow Cr_{(s)} ; \quad E^{\circ} = -0.740 \ V$
$2H^{+}_{(aq)} + 2e^{-} \rightarrow H_{2(g)} ; \quad E^{\circ} = 0.0 \ V$
$F_{2(g)} + 2e^{-} \rightarrow 2F^{-}_{(aq)} ; \quad E^{\circ} = 2.87 \ V$
Which of the following is the strongest reducing agent?

The standard electrode potentials of two half-cells are given as: $Ni^{2+}_{(aq)} + 2e^{-} \rightarrow Ni_{(s)}$; $E^o = -0.25 \ V$ and $Zn^{2+}_{(aq)} + 2e^{-} \rightarrow Zn_{(s)}$; $E^o = -0.76 \ V$. What is the standard $emf$ of the cell formed by connecting these two half-cells in $volt$?

For the cell $Zn_{(s)} | Zn^{2+}_{(aq)} || M^{x+}_{(aq)} | M_{(s)}$,different half cells and their standard electrode potentials are given below:

$M^{x+}_{(aq)} / M_{(s)}$	$Au^{3+}_{(aq)} / Au_{(s)}$	$Ag^{+}_{(aq)} / Ag_{(s)}$	$Fe^{3+}_{(aq)} / Fe^{2+}_{(aq)}$	$Fe^{2+}_{(aq)} / Fe_{(s)}$
$E^o M^{x+} / M (V)$	$1.40$	$0.80$	$0.77$	$-0.44$

If $E^o Zn^{2+}/Zn = -0.76 \ V$,which cathode will give a maximum value of $E^o_{cell}$ per electron transferred?

Given that $E^o_{K^{+}/K} = -2.93 \ V$,$E^o_{Fe^{2+}/Fe} = -0.44 \ V$,$E^o_{Zn^{2+}/Zn} = -0.76 \ V$,and $E^o_{Cu^{2+}/Cu} = 0.34 \ V$. Based on this data,which of the following is the strongest reducing agent?