Question

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

Answer 1

Answer:

Magnesium ribbon should be cleaned with sandpaper before burning in the air. ... 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

Answer 2

Answer:

Like rusting in case of iron, with magnesium, the oxide layer forms a white coating on the outside of the metal that will slow down or interfere with the burning process. Rubbing with sand paper helps to remove this oxide layer due to which burning speeds up.