Question

Explain in detail what happens when water is poured over Quicklime $\left(\mathrm{CaO}\right)$. Discuss all the physical observations and write the balanced chemical reaction involved.

Answer 1

Effect of water on quicklime:

1. When water is added to quicklime $\left(CaO\right)$ then, the temperature of the mixture changes.
2. A large amount of heat is liberated and a hissing sound is heard.
3. Heat liberation may lead to the boiling of water in the mixture.
4. The amount of heat produced shows that it is an exothermic reaction.
5. The reaction leads to the formation of slaked lime (calcium hydroxide) $\left(Ca{\left(OH\right)}_2\right)$.
6. It is an example of a combination reaction.

The complete balanced reaction:

$\underset{(Calciumoxide)}{\underbrace{CaO\left(s\right)}}+\underset{\left(Water\right)}{\underbrace{H_{2}O\left(l\right)}}\to \underset{(Calciumhydroxide)}{\underbrace{Ca{\left(OH\right)}_2\left(aq\right)}}+15,0000Calories\left(Heat\right)$