Question

When a water insoluble substance "X" is added to dil. HCL a colourless,odouless gas is evolved.when the gas is passed through lime water it turns milky.
Write the chemical formula of X and the chemical quation involved.

Answer 1

water insoluble substance is CaCO₃
CaCO₃(s)+ H₂SO₄(aq) = CaSO₄(aq)+H₂O(aq)+CO₂(g)
ca(oh)2+co2= caco3(milky)+h2o

Answer 2

The chemical formula of “X” involved in this reaction is $\mathrm{CaCO}_{3}$

The chemical reaction involved in this process is given below:

${CaCO}_{3}+2 {HCl} \rightarrow {CaCl}_{2}+2 {H}_{2} {O}+{CO}_{2}$

When a water insoluble substance "X" is added to dilute HCl, a colorless and odorless gas is evolved which turns lime water milky which indicates the gas evolved is carbon dioxide, as it turns lime water into milky solution. In other words, the substance X must be calcium carbonate. This is due to the fact that calcium carbonate is insoluble in water and release $CO_2 \ \mathrm{gas}$ with dilute acid like hydrochloric acid.

Carbon dioxide gas react with lime water to form calcium carbonate which is a white color solution.

$CO_2 \ (g) + Ca(OH)_2 \ (aq) \rightarrow CaCO_3 \ (s) + H_2O \ (l)$