A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

The correct option is B

HCl

Explanation for the correct answer:-

Option (B) HCl

• The egg shell is made up of Calcium carbonate$\left({\mathrm{CaCO}}_3\right)$.
• Therefore, when it reacts with Hydrochloric acid, it forms Calcium chloride, water, and Carbon dioxide.
• The complete reaction is:

$\underset{\mathrm{Calcium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Calcium}\mathrm{chloride}}{{\mathrm{CaCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)(\uparrow )}$

• The gas involved here is Carbon dioxide.
• This Carbon dioxide when reacted with Calcium hydroxide$\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$which is also called lime water, forms a milky solution of Calcium carbonate.
• This Calcium carbonate formed here is a white ppt, and along with it, water is also formed as a by-product.
• The complete reaction is:

$\underset{\mathrm{Calcium}\mathrm{hydroxide}(\mathrm{Lime}\mathrm{water})}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Calcium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)(\downarrow )\left(\mathrm{white}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Hence it is the correct option.

Therefore, option (B) HCl is the correct answer.