Question

why should magnesium ribbon should be clean before burning in air​

Answer 1

Magnesium ribbon should be cleaned with sandpaper before burning in the air. ... To remove the Magnesium oxide layer from the ribbon which may prevent or slow down the burning of magnesium ribbon. Unwanted impurities deposited on the magnesium ribbon can be removed and only pure magnesium can be used for the reaction.

Answer 2

Magnesium ribbon should be cleaned because it is kept in open air. It reacts with the oxygen in air and forms a thin layer of magnesium oxide on the outer layer. This magnesium oxide slows down the burning process and will hinder the experiment.

Hence, we have to remove impurities form the magnesium ribbon before performing any experiment.