Question

Mention any two observations when clean piece of magnesium ribbon is burnt in air

Answer 1

When a clean piece of Magnesium is burnt in Air it reacts to form Magnesium Oxide.
It is in the form of a white powder.
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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.