Question

A student took quicklime in a china dish and added a small amount of water to it. He would hear

• A. A pop sound
• B. A crackling sound
• C. A hissing sound
• D. No sound at all

Answer 1

The correct option is C

A hissing sound

The explanation for the correct answer: (c)

• Combination reactions: Reactions in which a single product is formed by the reaction of two or more reactants are called combination reactions. They are also called synthesis reactions. Bonds are formed during combination reactions and therefore, the majority of the combination reactions are exothermic.
• The reaction of quicklime with Water: Calcium oxide (CaO) is commonly called quicklime and it undergoes a combination reaction with Water (H₂O) to form Calcium hydroxide [Ca(OH)₂]. This reaction is highly vigorous and a large amount of heat is evolved.
• This reaction is called slaking of lime. The china dish gets heated during the reaction due to its exothermic nature. The increased heat in the china dish produces a hissing sound.
• The chemical equation for the reaction is:

$CaO\left(s\right)+H_{2}O\left(l\right)\to Ca{\left(OH\right)}_2\left(aq\right)$

(Calcium (Water) (Calcium hydroxide)

oxide)

Conclusion: Therefore, the correct option is (C) A hissing sound.