Question

Identify the catalyst used in the reaction between iodide and persulphate ions.

• A. \(\text{Cr}^{3+}\)
• B. \(\text{Fe}^{3+}\)
• C. \(\text{Ni}^{2+}\)
• D. \(\text{Fe}^{2+}\)

Hint:

In redox reactions, transition metal ions like \(\text{Fe}^{3+}\) and \(\text{Cr}^{3+}\) are often used as catalysts because they can easily undergo reversible oxidation and reduction reactions.

Answer 1

The Correct Option is B

The reaction between iodide (\(\text{I}^-\)) and persulphate ions (\(\text{S}_2\text{O}_8^{2-}\)) produces iodine (\(\text{I}_2\)) and sulphate ions (\(\text{SO}_4^{2-}\)): \[ 2 \text{I}^- + \text{S}_2\text{O}_8^{2-} \rightarrow \text{I}_2 + 2 \text{SO}_4^{2-} \] This is a redox reaction where iodide ions are oxidized to iodine. The persulphate ion (\(\text{S}_2\text{O}_8^{2-}\)) is reduced to sulphate ions. This reaction typically requires a catalyst to proceed efficiently. Among the options given, \(\text{Fe}^{3+}\) is the known catalyst for this reaction. The \(\text{Fe}^{3+}\) ion acts as an oxidizing agent, facilitating the oxidation of iodide ions to iodine. Thus, the correct catalyst is \(\text{Fe}^{3+}\), which is option (B)