"Manganese traffic light" experiment

Chem­i­cal traf­fic lights are se­ries of ex­per­i­ments in which light changes in the course of an ox­i­da­tion-re­duc­tion re­ac­tion. You can do this ex­per­i­ment at home,ob­serv­ing safe­ty rules.

Reagents and equip­ment:

• three glass­es;
• potas­si­um per­man­ganate;
• sug­ar (su­crose);
• sodi­um hy­drox­ide;
• dis­tilled wa­ter.

Step-by-step in­struc­tions

Dis­solve sev­er­al potas­si­um per­man­ganate crys­tals in 300 ml of wa­ter. Then dis­solve 10 g of sug­ar and 0.5 g of sodi­um hy­drox­ide in 50 ml of dis­tilled wa­ter. Mix the so­lu­tions of sug­ar and sodi­um hy­drox­ide. Pour the re­sult­ing mix­ture into the so­lu­tion of potas­si­um per­man­ganate. Ob­serve the change of col­or from pink to green to yel­low. If you wish to con­duct the ex­per­i­ment at home, you can use liq­uid for clean­ing pipes in­stead of the sodi­um hy­drox­ide so­lu­tion.

Pro­cess­es de­scrip­tion

Potas­si­um per­man­ganate is a strong ox­i­diz­er, as the man­ganese atom has a de­gree of ox­i­da­tion of +7, and de­pend­ing on the medi­um the per­man­ganate ion can re­duce to dif­fer­ing de­grees of ox­i­da­tion. In an al­ka­line medi­um, the per­man­ganate ion re­duces to a man­ganate ion with a de­gree of ox­i­da­tion of man­ganese +6, the aque­ous so­lu­tion of which has a green tint. The man­gan­ite ion then re­duces to man­ganese ox­ide (IV), which is brown, but as it is present in the so­lu­tion in the form of tiny par­ti­cles, the so­lu­tion turns yel­low.

Safe­ty pre­cau­tions

Wear gloves and pro­tec­tive glass­es when work­ing with al­ka­line so­lu­tions, as they may cause se­vere burns.

Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health. Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.