Question

what should a magnesium ribbon be cleaned before burning in air?

Answer 1

the magnesium ribbon which we usually use has a coating on white layer of magnesium oxide on its surface it is formed by the slow reaction of moist air on it these layer must be removed before burning

Answer 2

Magnesium ribbon reacts with oxygen in atmosphere to form magnesium oxide, which is a protective layer. The presence of this layer will result in ribbon burning very slowly. Hence, magnesium ribbon must be cleaned with a sand paper before burning.