Q. Why should a magnesium ribbon be cleaned before burning in air?
Answer: To burn a magnesium ribbon properly, it needs to be cleaned first because the layer of magnesium oxide (MgO) that forms on the ribbon’s surface when it reacts with oxygen in the air. This layer can stop the magnesium from burning brightly and evenly. By cleaning it, you ensure the ribbon burns well and shows its true, dazzling reaction.
Explanation & Example
Let’s break it down! Magnesium (Mg) is a shiny metal, but when it sits in the air, it slowly reacts with oxygen. This creates a thin, dull layer of magnesium oxide (MgO) on its surface. Think of it like a dusty coating on a mirror—it blocks the shine! This layer doesn’t burn the same way pure magnesium does, so it can make the experiment less exciting or even prevent proper burning.
To clean the ribbon, you gently rub it with sandpaper. This scrapes off the oxide layer, leaving the bright, pure magnesium ready to react with oxygen when heated. When you burn the cleaned ribbon, it catches fire easily and produces a brilliant white flame, along with white ash (magnesium oxide). If you skip cleaning, the flame might be weak or uneven because the oxide layer gets in the way.
Example: Imagine you’re trying to light a campfire with wet wood. The wet layer stops the fire from catching properly. But if you dry the wood first, it burns beautifully! Cleaning the magnesium ribbon is like drying the wood—it preps it for a great reaction.
