Question

Why should a magnesium ribbon be cleaned before it is burnt in the air?

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

Answer 1

Magnesium ribbon is cleaned with sandpaper before burning to remove the protective layer of magnesium oxide (MgO) that forms on its surface when it reacts with moist air. This oxide layer is stable and prevents or slows down the further burning of the magnesium ribbon. Removing this layer allows the pure magnesium metal to burn easily.

\[\ce{2Mg + O2 -> 2MgO}\]