Question

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> 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.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> 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.