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 <strong>correctly</strong>?

  1. A. CaO(s) + CO_{2}(g) \rightarrow CaCO_{3}(s)
  2. B. CaO(l) + CO_{2}(g) \rightarrow CaCO_{3}(s)
  3. C. Ca(OH)_{2}(l) + CO_{2}(l) \rightarrow CaCO_{3}(s) + H_{2}O(l)
  4. D. Ca(OH)_{2}(aq) + CO_{2}(g) \rightarrow CaCO_{3}(s) + H_{2}O(l)

Correct Answer: D. Ca(OH)_{2}(aq) + CO_{2}(g) \rightarrow CaCO_{3}(s) + H_{2}O(l)

Explanation

Slaked lime is an aqueous solution of calcium hydroxide Ca(OH)_2(aq), which reacts with carbon dioxide gas CO_2(g) to form solid calcium carbonate CaCO_3(s) and liquid water.

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