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GK QUESTION#3351

Which of the following chemical reactions takes place when quicklime reacts with water?

  1. ACaO(s) + H₂O(l) → Ca + H₂(aq)
  2. BC(s) + O₂(g) → CO₂(g)
  3. CCaO(s) + H₂O(l) → Ca(OH)₂(aq)Correct answer
  4. DCH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
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Answer

C. CaO(s) + H₂O(l) → Ca(OH)₂(aq)

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Explanation

Quicklime is calcium oxide, CaO. Adding water forms calcium hydroxide, Ca(OH)₂, and releases heat: CaO+H₂O→Ca(OH)₂. This is called slaking of lime and is a combination reaction. The aqueous notation represents dissolved calcium hydroxide; excess material can remain as a suspension because its solubility is limited.

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