Question 4 - MCQs from NCERT Exemplar - Chapter 1 Class 10 - Chemical Reactions and Equations

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

Exo means out and thermic means heat . 

Here

1. Reaction of water with quicklime - Heat is released. So, it is exothermic
2. Dilution of an acid - When acid is diluted, Heat is released. So, it is exothermic
3. Evaporation of water - Heat needs to be absorbed for this reaction to take place. So, it is endothermic.
4. Sublimation of camphor (crystals) - For sublimation to take place, heat needs to be absorbed. So, it is endothermic.

Thus, reaction of water with quicklime and dilution of acid are exothermic reactions.

So, the correct option is (a) - (i) and (ii)