A solution reacts with crushed egg-shells to give a gas that turns limewater milky

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1

A solution reacts with crushed egg-shells to give a gas that turns limewater milky

2

Egg shells contains calcium carbonate, which on reaction with HCl liberates CO2 gas which turn lime water to milky.
CaCO3 + 2HCl → CaCl2 + H2O + CO2