Question

Question 4

Which of the following are exothermic processes?

(i) Reaction of water with quicklime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)

Answer 1

Option (a) is correct.

When quick lime reacts with water, a large amount of heat is released along with the formation of calcium hydroxide. The reaction occurs as follows:

$\text{CaO}+{\text{H}}_2\text{O}\to {\text{Ca(OH)}}_2+\text{Heat}$

Similarly, the process of dissolving an acid or base in water is a highly exothermic process. Evaporation of water and sublimation of camphor are endothermic reactions, since in both cases heat energy is absorbed from the surroundings.