Question

why should a magnesium riboon be clean before burning it in air ?

Answer 1

A layer of oxide is been deposit it is cleaned with the Sandpaper so that it could be easily Bond in the presence of oxygen

Answer 2

magnesium is reactive metal so when it kept in open air, it slowly started reacting with oxygen and form a layer of magnesium oxide (MgO) on the surface of the magnesium metal these layer on magnesium metal of magnesium oxide is quite stable,which prevents the further reaction of oxygen with the metal.

that's why before the reaction the magnesium ribbon rubbed with sand paper which removes the layer from metal . then again magnesium ribbon burnt in air and takes place the reaction.

i hope this will help you

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