Question

Why should a magnesium ribbon be cleaned before burning in air?​

Answer 1

$\huge \frak \pink{Answer}$

This is because, magnesium ribbon already has a layer of oxide over it. i.e a layer of MgO is always present on the metal. hence, it is necessary to remove that oxide layer with the help of a sand paper in order to do the 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.