Presentation on theme: "Alkaline permanganate and hydrogen sulfite. In the HSO 3 - ion, sulfur is in the +4 oxidation state. Sodium hydrogen sulfite is a white solid which dissolves."— Presentation transcript:
Alkaline permanganate and hydrogen sulfite
In the HSO 3 - ion, sulfur is in the +4 oxidation state. Sodium hydrogen sulfite is a white solid which dissolves in water to form a colourless solution.
Sodium hydroxide solution is added to make the solution alkaline.
Purple potassium permanganate solution is added. The purple solution turns green.
MnO e - → MnO 4 2-
The alkaline solution is acidified by adding hydrochloric acid. The green solution turns brown, then orange, and finally colourless as the excess HSO 3 - further reduces the green MnO 4 2- to brown MnO 2 and then colourless Mn 2+.
Finally we add barium chloride solution, which reacts to form a white precipitate. This confirms that the HSO 3 - has been oxidised to SO The solution had to be acidified first, because Ba(OH) 2 is only slightly soluble.
MnO e - → MnO 4 2- purple green HSO H 2 O → SO H + + 2e - 2MnO HSO H 2 O → 2MnO SO H +