Which of the following gas readily de-colourises the acidified KMnO\(_4\) solution?
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When performing reactions with KMnO\(_4\), always consider whether the reactant is a reducing agent that can reduce the manganese ion from +7 to +2, such as SO\(_2\).
The reaction of acidified KMnO\(_4\) with a reducing agent like sulfur dioxide (SO\(_2\)) decolorises the purple color of the permanganate solution by reducing Mn\(^7+\) to Mn\(^2+\). This is a classic example of a redox reaction where KMnO\(_4\) acts as an oxidizing agent and SO\(_2\) as the reducing agent.
- SO\(_2\) readily decolourises acidified KMnO\(_4\) solution by reducing manganese from its +7 oxidation state to +2.
Thus, the correct answer is SO\(_2\).