Question

When air is blown inside a test tube containing limewater, the limewater in it turns milky. What does this indicate?

• A. The air that we blow is dirty.
• B. The air that we blow contains oxygen.
• C. The air that we blow contains carbon dioxide.
• D. Lime water is always milky.

Answer 1

The correct option is C The air that we blow contains carbon dioxide.

During cellular respiration, oxygen is consumed and carbon dioxide is liberated. This carbon dioxide is present in the air that we exhale. When we blow into a test tube containing limewater (calcium hydroxide), the carbon dioxide reacts with it and turns it milky. This milky appearance is due to the formation of calcium carbonate.