Virtual CrezLab - Qualitative Analysis - Redox Reactions/Displacement

Since a reducing agent is oxidised by an oxidising agent during a redox reaction, an oxidizing agent is often used as a reagent to test for a reducing agent.

Example 2: Acidified Potassium mangante(VII) is an oxidising agent added to test for reducing agents.

2. To a portion of unknown solution B add an equal amount of dilute sulphuric acid followed by potassium manganate(VII) solution.

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Observation

Identity of product

Type of reaction

Purple potassium manganate(VII) decolourises.

Colourless solution of manganese(II) ions, Mn²⁺ formed.

Redox reaction.

Solution B contains a reducing agent. Purple manganate(VII) ions, MnO₄^- is reduced by solution B to colourless Mn²⁺ ions.

Manganate(VII) ions, MnO₄^- have lost oxygen atoms and gained electrons to form Mn²⁺ ions.The oxidation number of manganese decreased from +7 in KMnO₄ to +2 in Mn²⁺ ions.

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