Question

Which of the following is Exothermic in nature?

• A. Electrolysis of water
• B. Conversion of limestone into quick lime
• C. Process of respiration
• D. Process of photosynthesis

Answer 1

The correct option is C

Process of respiration

The explanation for the correct option:

(C) Process of respiration

1. Respiration is an exothermic process because the breakdown of glucose in the presence of oxygen releases energy.
2. ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{aq}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right)\to 6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+6{\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{Energy}$

The explanation for incorrect options:

(A) Electrolysis of water

1. Water is converted to hydrogen and oxygen using heat energy in the electrolysis process.
2. $2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$
3. It is an endothermic reaction.

(B) Conversion of limestone into quick lime

1. The conversion of limestone to quicklime can be accomplished by heating it.
2. ${\mathrm{CaCO}}_3\left(\mathrm{aq}\right)\to \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$
3. Then, it is an endothermic reaction.

(D) Process of photosynthesis

1. Light energy is used in the photosynthesis process to transform carbon dioxide and water into glucose and oxygen.
2. $6{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{aq}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right)$
3. It is an endothermic reaction.

Hence, the correct option is (C).