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Standard electrode potentials are used for various processes:

• It is used to measure relative strengths of various oxidants and reductants.
• It is used to calculate standard cell potential.
• It is used to predict possible reactions.

A set of half-reactions (in acidic medium) along with their standard reduction potential, $E^\circ ($in volt$)$ values are given below:
$I_2 + 2e^- \rightarrow 2I^- ; E^\circ = 0.54 V$
$Cl_2 + 2e^- \rightarrow 2Cl^- ; E^\circ = 1.36 V$
$Mn^{3+} +e^- \rightarrow Mn^{2+}; E^\circ = 1.50 V$
$Fe^{3+} + e^- \rightarrow Fe^{2+}; E^\circ = 0.77 V$
$O_2 + 4H^+ + 4e^- \rightarrow 2H_2O ; E^\circ = 1.23 V$
The following questions are multiple choice questions. Choose the most appropriate answer:

1. Which of the following statements is correct?

1. $Cl^-$ is oxidised by $O_2.$
2. $Fe^{2+}$ is oxidised by iodine.
3. $I^-$ is oxidised by chlorine.
4. $Mn^{2+}$ is oxidised by chlorine.

2. $Mn^{3+}$ is not stable in acidic medium, while $Fe^{3+}$ is stable because:

1. $O_2$ oxidises $Mn^{2+}$ to $Mn^{3+}$
2. $O_2$ oxidises both $Mn^{2+}$ to $Mn^{3+}$ and $Fe^{2+}$ to $Fe^{3+}$
3. $Fe^{3+}$ oxidises $H_2O$ to $O_2$
4. $Mn^{3+}$ oxidises $H_2O$ to $O_2$

3. The strongest reducing agent in the aqueous solution is:

1. $I^-$
2. $Cl^-$
3. $Mn^{2+}$
4. $Fe^{2+}$

4. The emf for the following reaction is:

$\text{I}_2+\text{KCl}\rightleftharpoons2\text{KI}+\text{Cl}_2$

1. $-0.82\ V$
2. $+0.82\ V$
3. $-0.73\ V$
4. $+0.73\ V$

5. Which of the following statements is correct for the following reaction?

$Fe^{3+} + Mn^{2+} \rightarrow Fe^{2+}+ Mn^{3+}$

1. The emf of the cell is positive.
2. $Fe^{3+}$ oxidises $Mn^{2+}.$
3. The reaction does not occur.
4. All are correct.