Question

1. Briefly state the importance of the following constituents of air :

(c) Carbon dioxide

Answer 1

The percentage of carbon dioxide in the air, by volume, varies from 0.03% to 0.04%. The areas where a lot of fuel burns have more percentage of carbon dioxide.

Importance of carbon dioxide in the atmosphere

(i) It manufactures food for plants. The plants take in carbon dioxide and absorb water from the soil. it uses these two components in the presence of sunlight to produce glucose and oxygen as products of photosynthesis. The oxygen which plants give out during photosynthesis is used by humans during respiration.

$\underset{\mathrm{Carbon}\mathrm{dioxide}\mathrm{Water}\mathrm{Glucose}\mathrm{Oxygen}}{6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}\underset{\mathrm{Photosynthesis}}{\overset{\mathrm{Sunlight}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2}$

(ii) Carbon dioxide is used to extinguish fires. Carbon dioxide gas is filled in the extinguisher to act as an insulator from oxygen and cut off the supply of air to the fire. Some fire extinguishers, especially those designed for electrical fires, contain liquid carbon dioxide under pressure.

(iii) Carbon dioxide dissolved in water is capable of dissolving rocks with calcium carbonate (chalk) or magnesium carbonate as components. The salts formed after dissolution are calcium bicarbonate and magnesium bicarbonate. These minerals give taste to natural water as well act as important minerals for the growth of plants

$\underset{\mathrm{Calcium}\mathrm{carbonte}\mathrm{Water}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Calcium}\mathrm{biocarbonate}}{{\mathrm{CaCO}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2\to \mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2}$

$\underset{\mathrm{Magnesium}\mathrm{carbonte}\mathrm{Water}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Magnesium}\mathrm{biocarbonate}}{{\mathrm{MgCO}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2\to \mathrm{Mg}{\left({\mathrm{HCO}}_3\right)}_2}$.