Question

Why should a magnesium ribbon be rubbed before burning in air

Answer 1

Answer:

it should clean to remove oxide layer formed on it so that reaction should be clear

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.