Question

why should magnesium ribbon Ribbon is cleaned before burning in air

Answer 1

I hope this may help you

Answer 2

$<bullet> Magnesium is a very reactive metal. When stored, it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper for removing this layer so that the underlying metal can be exposed to air.$