Question

When the gas formed on heating limestone is passed through freshely prepared limewater turns milky

Answer 1

               Answer

• The gas that is formed when limestone is heated is Carbon dioxide ( Co₂) .

• The reaction that takes place when limestone is heated is decomposition reaction.

$\bigstar$ Limestone is Calcium Carbonate  (CaCO₃) , which on heating decomposes to form Calcium Oxide or quicklime  is obtained along with Carbon dioxide gas .

Equation of decomposition of Limestone

(Limestone) CaCO₃ $\longrightarrow$ CaO(Quicklime) + CO₂ (Carbon dioxide )

$\bigstar$ When Carbon dioxide is passed through Lime water or Calcium Hydroxide or Ca(OH)₂ , the lime water turns milky because it forms Calcium Carbonate which is a whitish precipitate .

Equation when CO₂ is passed through Calcium Hydroxide

Ca(OH)₂ + CO₂ (Carbon dioxide ) $\longrightarrow$ CaCO₃ + H₂O