Magnesium ribbon should be cleaned with sandpaper before burning in the air because of the following reasons:
- Magnesium very reactive element which rapidly reacts with oxygen in the air to form a white layer of magnesium oxide and this layer will not burn.
- 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.