Question

why should magnesium ribbon be cleaned before burning air

Answer 1

hey user here is your answer :-
when exposed to air for a long time magnesium develops a layer of oxide on it. when it is used for experiment oxide being a stable compound prevents further reaction of magnesium with oxygen .it is cleaned to remove the layer of oxide from it (magnesium ribbon).
cleaning a magnesium ribbon is also good from a safety point of view .we should clean it because our eyes can get affected when magnesium oxide is burnt . so, we should clean magnesium ribbon with a sand paper .

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.