Question

The most commonly used experiment to detect the release of $CO_2$
A. Exhaling test
B. Lime water test
C. Mercury test
D. None of the above

Answer 1

Carbon dioxide could be a colourless gas with high density than that of the dry air. It is a greenhouse gas present in the atmosphere. The calcium hydroxide and water are used in this experiment.

Complete answer: In the chemical reaction, firstly, the lime water reacts with carbon dioxide ($CO_2$) in a two-step process, Generally, the limewater is calcium hydroxide dissolved in water.
Ca(OH)_2 + H_2O → $$$$C{a^{ + + }} + 2OH - . After that, the $C{a^{ + + }}$ reacts with $CO_2$ to give calcium carbonate, which is mostly insoluble in water.
Ca(OH)_2$$$$ + $CO_2$ $→ CaCO_3 + H2O$ ($CaCO_3$ will lead to precipitate, creating a white milky solution).
Even In the presence of more, or excess of $CO_2$, the $CaCO_3$ reacts with more $CO_2$ to give calcium bicarbonate, which is water-soluble generally.
CaCO_3$$$$ + CO_2$$$$ → Ca(HCO_3)$$$$ + $H_2O$
Moreover, the milky appearance of $C{a^{ + + }}$ goes away as the insoluble $CaCO_3$ reacts forming the soluble $Ca(HCO_3)_2$. The above chemical reactions are commonly used to test the presence of carbon dioxide in gaseous samples in school laboratories and sugar refining in a process called carbonatation.
Hence, option B is the correct answer.

Note: Adding lime to $H_2O$, increases the pH scale, boosting seawater's ability to soak up $CO_2$ from the air and reducing the tendency to unleash it back once more. However, adding lime to $H_2O$ absorbs the maximum amount of $CO_2$.