Question

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

Answer 1

Magnesium ribbon should be cleaned before burning because it may contain layers of oxides and rust which needs to be removed.
Metals reacts with gases when left open.
Hence it needs to be cleaned with sandpaper for better use.

Hope it helps.

Have a good day buddy.

Answer 2

magnesium ribbon should be cleaned before burning in air to remove the layer of magnesium oxide from its surface . so that it can burn smoothly in the air