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Alkaline permanganate and hydrogen sulfite

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Presentation on theme: "Alkaline permanganate and hydrogen sulfite"— Presentation transcript:

1 Alkaline permanganate and hydrogen sulfite

2 In the HSO3- ion, sulfur is in the +4 oxidation state.
Sodium hydrogen sulfite is a white solid which dissolves in water to form a colourless solution.

3 Sodium hydroxide solution is added to make the solution alkaline.

4 Purple potassium permanganate solution is added.
The purple solution turns green.

5 MnO4- + e- → MnO42-

6 The alkaline solution is acidified by adding hydrochloric acid.
The green solution turns brown, then orange, and finally colourless as the excess HSO3- further reduces the green MnO42- to brown MnO2 and then colourless Mn2+.

7 Finally we add barium chloride solution, which reacts to form a white precipitate. This confirms that the HSO3- has been oxidised to SO42-. The solution had to be acidified first, because Ba(OH)2 is only slightly soluble.

8 MnO e- → MnO42- purple green HSO H2O → SO H e- 2MnO HSO H2O → 2MnO SO H+

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