Question

When water is added to compound (A) of calcium , solution of compound (B) is formed . When carbon dioxide is passed into the solution , it turns milky due to the formation of compound (C) . If excess of carbon dioxide is passed into the solution , milkiness disappears due to the formation of compound D. Identify the compounds A , B , C and D . Explain why the milkiness disappears in the last step .

Answer 1

When `CO_(2)` is passed through solution of compound (B) , it turns milky , therefore , solution of compound (B) must be lime water , i.e., `Ca(OH)_(2)` solution and milkiness must be due to the formation of insoluble `CaCO_(3)` (C) . Further since , compound (B) is obtained by dissolving compound (A) in water , therefore , compound (A) must be quick lime , CaO
`underset((A)) underset("Calcium oxide")(CaO) + H_(2)O underset("Lime water (B)")(Ca(OH)_(2)) , CO_(2) to underset("Milkiness)")underset("carbonate (C)")underset("Calcium")(CaCO_(3)) + H_(2)O`
When excess of `CO_(2)` is passed milkiness disappears due to formation of soluble calcium bicarbonate (D)
`underset("Milkiness (C)")(CaCO_(3)) + CO_(2) + H_(2)O to underset("(Soluble in" H_(2)O")") underset("Calcium bicarbonate")(Ca(HCO_(3))_(2))`
Thus , compound (A) = CaO , Compound (B) = `Ca(OH)_(2)` , Compound (C) = `CaCO_(3)` and compound (D) = `Ca(HCO_(3))_(2)`.