Question

Q7) On passing excess CO2 through lime water, it first turns

milky and then becomes colourless. Explain why? Write

chemical equations.​

Answer 1

Answer:

When CO2 is passed through lime water , the lime water turns milky white due to formation of white precipitate of calcium carbonate.

Ca(OH)2 (aq) +CO2 -----> CaCO3 (s) +H2O(l)

If excess of Carbon dioxide is passed through lime water, then the white precipitate formed dissolves due to formation of a soluble salt calcium hydrogencarbonate and the solution becomes clear again.

CaCO3 + CO2(g) +H2O(l) --------> Ca(HCO3)2(aq)

Answer 2

When Calcium Hydroxide (Slaked lime) reacts with carbon dioxide than it first turns milky because of the formation of a white precipitate which is insoluble in water.

Ca(OH)2 + CO2 → CaCO3 + H2O

When an excess of carbon dioxide is passed through Slaked lime then the white precipitate gets dissolved and then carbon dioxide reacts with Calcium Carbonate. Due to this formation of Calcium hydrogen-carbonate (which is colourless and soluble in water) And the solution becomes clear again.

CaCO3 + CO2 + H2O → Ca(HCO3)2