Question

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

Answer 1

Magnesium is a very reactive metal. When it is kept in the open air it can react with the gases present in the air. Cleaning will remove those impurities formed due to the reaction with air.

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Answer 2

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→ A magnesium Ribbon must be cleaned before burning in air because magnesium when exposed to air reacts with oxygen which leads to the formation of magnesium oxide on the surface of magnesium ribbon.