Question

why should a magnesium ribbon be cleaned before burning 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

♤ When Magnesium ribbon is exposed in the atmosphere it form a layer of magnesium oxide on its surface.

♤ This layer of magnesium oxide is stable compound to prevent further reaction of magnesium with oxygen.

♤ Hence, it should be cleaned before burning in air to remove this layer so that the metal can be exposed to air properly.