Chemistry 2005 JAMB Past Questions - Question 13: he decolourization of the purple colour of tetraoxomanganate (VII) ion is a test for

Correct Answer

A

Explanation

The decolorization of the purple color of the tetraoxomanganate(VII) ion, also known as permanganate ion (MnO₄⁻), is a test for the presence of reducing agents in a solution.

The permanganate ion is a strong oxidizing agent, and its characteristic purple color arises from the absorption of light in the visible spectrum. When a reducing agent is present in the solution, it can react with the permanganate ion, causing it to be reduced to colorless manganese(II) ion (Mn²⁺). This reduction results in the decolorization of the solution.

The balanced chemical equation for the reaction between permanganate ion and a reducing agent in an acidic medium is typically represented as follows:

\[ \ce{5e^{-} + 8H+ + MnO4- -> Mn^2+ + 4H2O} \]

In this equation, \( e^{-} \) represents electrons, and \( H+ \) represents protons (acidic conditions are assumed). The reducing agent donates electrons to the permanganate ion, reducing it to colorless manganese(II) ions.

This test is commonly used in analytical chemistry to identify and quantify reducing agents in a sample. The disappearance of the purple color is a visual indication that the reaction has occurred, and the extent of decolorization can be correlated with the amount of reducing agent present.