The following reactions represent the reduction of IO3^- ion into I^- ion in acidic and basic medium — Electrochemistry Chemistry Question

💡 Solution & Explanation

\noindent\textbf{Question Reference:} ch08/exI/Q30 \subsection*{Step 1 - Understand the Principle of Oxidizing Power and Reduction Potential} An oxidizing agent is a chemical species that oxidizes other substances by accepting electrons, meaning it undergoes reduction itself. The tendency of a species to gain electrons and get reduced is quantitatively measured by its standard reduction potential ($E^\circ$). A higher, more positive standard reduction potential indicates a stronger thermodynamic drive to gain electrons. Consequently, the species will act as a stronger and more effective oxidizing agent in the medium where its standard reduction potential is higher. \subsection*{Step 2 - Analyze the Given Half-Reactions} We are given two half-reactions for the reduction of iodate ion (\ce{IO3-}) to iodide ion (\ce{I-}): \begin{enumerate} \item \textbf{Acidic Medium:} $$\ce{IO3- + 6H+ + 6e- -> I- + 3H2O} \quad E^\circ = +0.907\text{ V}$$ \item \textbf{Basic Medium:} $$\ce{IO3- + 3H2O + 6e- -> I- + 6OH-} \quad E^\circ = +0.260\text{ V}$$ \end{enumerate} \subsection*{Step 3 - Compare the Standard Reduction Potentials} We compare the standard reduction potential values ($E^\circ$) in both media: $$E^\circ_{\text{acidic}} = +0.907\text{ V}$$ $$E^\circ_{\text{basic}} = +0.260\text{ V}$$ Since $+0.907\text{ V} > +0.260\text{ V}$, the standard reduction potential for the reduction of \ce{IO3-} is significantly higher in the acidic medium than in the basic medium. \subsection*{Step 4 - Evaluate the Options} \begin{itemize} \item \textbf{Option (A) is correct:} Because $E^\circ$ is higher in the acidic medium ($+0.907\text{ V}$), \ce{IO3-} has a much stronger tendency to accept electrons and undergo reduction. Therefore, it is a significantly better oxidizing agent in an acidic medium. \item \textbf{Option (B) is incorrect:} In a basic medium, the reduction potential is much lower ($+0.260\text{ V}$), meaning the drive to accept electrons is weaker, making it a poorer oxidizing agent compared to the acidic medium. \item \textbf{Option (C) is incorrect:} Since the reduction potential values in the two media are vastly different, the oxidizing power is not equal in both media. \item \textbf{Option (D) is incorrect:} The relative oxidizing power is highly predictable using the provided standard reduction potential values. \end{itemize} \noindent\textbf{Correct Option:} \textbf{(A)}