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

Answer. Magnesium is a metal with a high reactivity. It can react with the gases in the air if it is left out in the open. Cleaning will remove any pollutants that have accumulated as a result of the reaction with the air.

• Magnesium is a metal that belongs to the alkaline earth family. Alkaline earth metals are metals that belong to the second group of the periodic table. Because they only contain two electrons in their outer electron shell, they are extremely reactive
• Because of the high reactivity of magnesium, it is recommended that magnesium ribbons be cleaned before use
• When a magnesium ribbon is exposed to air for an extended period of time, it reacts with the oxygen in the air, converting the magnesium ribbon to magnesium oxide

2Mg+O₂→2MgO 

• The oxide coating on the magnesium ribbon forms on the ribbon’s surface, turning the ribbon white. Because this layer does not burn easily, it prevents the ribbon from being burned
• So, since the oxide layer prevents the remove from burning, we must remove it. To accomplish so, we must first wipe the ribbon’s surface. Cleaning the surface of the magnesium ribbon removes the oxide layer, allowing the ribbon to burn more effectively and achieve the desired result
• The magnesium ribbon emits strong heat and a dazzling white light when it burns in the air. Magnesium oxide is formed when oxygen from the air combines with magnesium. The reaction is the same as the one described above:

2Mg+O₂→2MgO.