a.When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky

Question

4. Give scientific reasons. a.When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky

Answer 1

i. When limestone (CaCO₃) is heated; it undergoes decomposition reaction giving calcium oxide (CaO) and carbon dioxide (CO₂) as products.

ii. When this carbon dioxide gas is passed through freshly prepared limewater, it forms insoluble calcium carbonate as the product, because of which lime water turns milky.

iii. The reaction takes place in the following steps: CaCO₃(s) → CaO(s) + CO₂↑ (Heating of limestone) Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O (On passing carbon dioxide gas through limewater)
iv. Hence, when the gas formed on heating limestone is passed through freshly prepared limewater the limewater turns milky.