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).

The correct option is B

(1) and (3)

The correct option is B.

Explanation the correct option:

Exothermic reactions:

• The reactions in which the heat energy is given out during the reaction are called exothermic reactions.
• The enthalpy change of an exothermic reaction is negative.

Dilution of an acid:

The dilution of an acid with water is an exothermic reaction as it evolves heat energy.

Example:

The dilution of sulphuric acid with water is an exothermic process.

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

Reaction of water with quicklime:

• Calcium oxide (quick lime) reacts with water to form calcium hydroxide.
• This reaction releases an enormous amount of energy. Hence, it is an exothermic reaction.

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

Explanation the incorrect option:

Evaporation of water:

• Evaporation is an endothermic process as water must absorb heat from the surroundings to increase its kinetic energy.
• Ex: Sweat which cools the human body as it evaporates from the skin.

Sublimation of camphor crystals:

• The process of changing a solid to gas without becoming liquid is called sublimation.
• The sublimation process takes place by absorbing the heat. Hence, the sublimation of camphor is an endothermic reaction.

Final answer: Dilution of acid and reaction of water with quicklime are exothermic processes.