Question

why should a magnesium ribbon be cleaned before burning in air

Answer 1

Magnesium ribbon is cleaned before burning in air so that the layer of magnesium oxide (which is formed due to reaction of magnesium with air) can be removed in order to get the desired chemical reaction.

Answer 2

Heya!

I'm simple words magnesium ribbon be cleaned before burning in air in order to prevent oxidation by reaction of magnesium in oxygen present in the air & get the desired chemical

Hope this helps!
Good day mate.
~@Nikki❤