Question

If you exhale multiple times into a conical flask containing lime water through a single inlet fixed through a stop cork, lime water will
A. Become cooler
B. Turn milky
C. Remain unchanged
D. Turn yellow

Answer 1

Hint: Lime water is obtained by slacking of quicklime which becomes lime. The Lime water test is a simple and straightforward technique used to test for the presence of $CO_2$. The exhaled $CO_2$ is employed to supply a precipitate of carbonate with the lime water.

Complete answer: $CO_2$ is usually found in its gaseous form and is a major constituent part of the plant and animal life cycle. $CO_2$ is consumed by plants in photosynthesis and is produced by animals during cellular respiration.
When $CO_2$ is introduced to lime water for a brief time, it turns the lime water milky; this happens due to the formation of a white precipitate of carbonate.

So, the correct answer is option B. Turn milky.

Note: Tube of the entire apparatus that contains the inhaled air is generally less milky in appearance while the tube containing the exhaled air is milkier relatively.
This concludes that less amount of $CO_2$ is present in inhaled air but far more $CO_2$ is present in exhaled air.