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ICSE Class 9 Chemistry Question 26 of 55

ICSE Questions Set in Previous Years — Question 26

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Question 26

State your observations and give balanced equations of the reactions when carbon dioxide is passed through clear lime water (a) for a short time (b) for a long time.

Answer

(a) When carbon dioxide is passed through lime water for a short time, it turns lime water milky. This is due to the formation of insoluble calcium carbonate.

Ca(OH)2 + CO2 ⟶ CaCO3 ↓ + H2O

(b) When the gas is passed for a long time, the milkiness disappears. This is due to the formation of a soluble bicarbonate.

CaCO3 + CO2 + H2O ⟶ Ca(HCO3)2 [soluble]