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

Hint: 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 \[CO_2\].