Question

Which of the following are exothermic processes?

(1) Dilution of an acid.

(2) Evaporation of water.

(3) Reaction of water with Quicklime.

(4) Sublimation of camphor (crystals).

• A. (1) and (2)
• B. (1) and (3)
• C. (1) and (4)
• D. (3) and (4)

Answer 1

The correct option is B

(1) and (3)

The correct option is B.

Explanation for correct option

Step 1: Calcium hydroxide is created when water combines with quick lime, coupled with the evolution of heat. As a result, it is an exothermic.

$\mathrm{CaO}+{\mathrm{H}}_2\mathrm{O}⟶\mathrm{Ca}{\left(\mathrm{OH}\right)}_2+\mathrm{Heat}$

Step 2: Diluting a concentrated acid is a very exothermic process.

${\mathrm{H}}_2{\mathrm{SO}}_4+{\mathrm{H}}_2\mathrm{O}⟶{\mathrm{H}}_3{\mathrm{O}}^{+}+{{\mathrm{HSO}}_4}^{-}+\mathrm{Heat}$

Explanation for incorrect option

Option A: (1) and (2)

1. ${\mathrm{H}}_2{\mathrm{SO}}_4+{\mathrm{H}}_2\mathrm{O}⟶{\mathrm{H}}_3\mathrm{O}++{{\mathrm{HSO}}_4}^{-}+\mathrm{Heat}$ is an exothermic reaction.
2. Evaporation of water is an endothermic reaction.

Option C: (1) and (4)

1. Sublimation is the technique by which a material transitions from solid to gas without becoming liquid.
2. Thus, thermal energy is required for camphor sublimation. As a result, it is an endothermic reaction.

Option D: (3) and (4)

1. Calcium hydroxide is formed when it reacts with water. The interaction of water with quicklime produces a lot of energy. As a result, this is an exothermic process.
2. Thermal energy is required for camphor sublimation. As a result, it is an endothermic reaction.

Final answer: Dilution of an acid and Reaction of water with Quicklime are exothermic processes.