Question

Why is magnesium ribbon cleaned before burning it in air

Answer 1

Magnesium ribbon must becleaned before burning in air so that the layer of magnesium oxide (which is formed due to reaction of magnesiumwith air) can be removed in order to get the desired chemical reaction.

Answer 2

Answer :

Magnesium is a highly reactive metal. When exposed to air for a long time it gets coated with the layer of oxide which is physically and mentally stable and therefore, partly masks the reactivity of magnesium. The oxide coating does not burn when a flame is brought in contact with the metal. Therefore, the surface should be cleaned, with a sandpaper before burning the magnesium ribbon in air.