Q: During white-washing of walls, slaked lime reacts slowly with carbon dioxide in air to form a thin layer of calcium carbonate on the walls. Which of the following reactions represents this correctly?
(a)CaO (s) + CO₂ (g) → CaCO₃ (s)
(b)CaO (l) + CO₂ (g) → CaCO₃ (s)
(c)Ca(OH)₂ (l) + CO₂ (l) → CaCO₃ (s) + H₂O (l)
(d)Ca(OH)₂ (aq) + CO₂ (g) → CaCO₃ (s) + H₂O (l)
Correct Answer: (d)
The correct answer is (c) 'Ca(OH)2(l) + CO2(g) → CaCO3(s) + H2O(l)'. This question from the Environment & Ecology domain tests knowledge of Climate Change & Greenhouse Gases.