Question

Complete and balance the following chemical equations: (a) \[ 2MnO_4^-(aq) + 10I^-(aq) + 16H^+(aq) \rightarrow \] (b) \[ Cr_2O_7^{2-}(aq) + 6Fe^{2+}(aq) + 14H^+(aq) \rightarrow \] 

Hint:

In redox reactions, the oxidizing agent is reduced, and the reducing agent is oxidized. Pay attention to the stoichiometric coefficients when balancing the equation.

Answer 1

Oxidation-Reduction Reactions 

(a) Reaction of Permanganate with Iodide Ions

In an acidic solution, permanganate ions (\( \text{MnO}_4^- \)) act as an oxidizing agent and oxidize iodide ions (\( I^- \)) to iodine (\( I_2 \)). The balanced equation for this reaction is as follows:

\[ 2 \, \text{MnO}_4^-(aq) + 10 \, \text{I}^-(aq) + 16 \, \text{H}^+(aq) \rightarrow 2 \, \text{Mn}^{2+}(aq) + 5 \, \text{I}_2(aq) + 8 \, \text{H}_2\text{O}(l) \]

In this reaction, permanganate ions are reduced to \( \text{Mn}^{2+} \), and iodide ions are oxidized to iodine.

(b) Reaction of Dichromate with Iron(II) Ions

In an acidic solution, dichromate ions (\( \text{Cr}_2\text{O}_7^{2-} \)) are reduced to chromium(III) ions (\( \text{Cr}^{3+} \)), while iron(II) ions (\( \text{Fe}^{2+} \)) are oxidized to iron(III) ions (\( \text{Fe}^{3+} \)). The balanced equation for this reaction is:

\[ \text{Cr}_2\text{O}_7^{2-}(aq) + 6 \, \text{Fe}^{2+}(aq) + 14 \, \text{H}^+(aq) \rightarrow 2 \, \text{Cr}^{3+}(aq) + 6 \, \text{Fe}^{3+}(aq) + 7 \, \text{H}_2\text{O}(l) \]

In this reaction, the dichromate ions are reduced to \( \text{Cr}^{3+} \), and iron(II) is oxidized to iron(III).