Question

Which of the following constituent gas is not directly used by the living beings?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide

Answer 1

The earth’s atmosphere is a blanket of gases that surrounds the earth. There are many gases which are present in the earth’s atmosphere and are essential for living beings. These gases are directly or indirectly used by living beings. Some of these gases are- Nitrogen (78 percent), Oxygen (21 percent), Argon (0.93 percent), Carbon dioxide (0.04 percent), and some traces amount of neon, helium, methane, krypton, and hydrogen as well as water vapor.

Complete step by step answer:
oxygen is the main constituent gas which is most essential for the living beings for their existence on the earth. The life system on earth completely depends on the oxygen which is present in the earth’s atmosphere. Since the amount of nitrogen (78 percent) gas is more in the atmosphere but it cannot be used by the living beings directly instead of oxygen.
Therefore, nitrogen gas in the atmosphere cannot be used directly by living beings.

So, the correct answer is Option B .

Note: Nitrogen is a group of 15 elements of the p- block elements of the periodic table. Its atomic number 7 and its electronic configuration is $1{s^2}2{s^2}2{p^3}$.

Nitrogen occurs in the free state as well as in the combined state. In the free state, it occurs as dinitrogen $\left( {{N_2}} \right)$ . Air is the most abundant source of free nitrogen. It is also present in the volcanic gases and the gases produced by the burning of coal. The gases from mineral sources have been found to contain $95\%$ nitrogen.

In the combined state, it occurs as nitrates and it is also an essential constituent of all proteins found in animals and plants.In the laboratory, dinitrogen is prepared by a heating equimolar aqueous solution of sodium nitrite and ammonium chloride in a round bottom flask. The reaction involved in this process is written below:

$N{H_4}Cl + NaN{O_2} \to N{H_4}N{O_{_2}} + NaCl$

$N{H_4}N{O_{_2}} \to {N_2} + 2{H_2}O$

Small amounts of NO and $HN{O_3}$ are also formed in the reaction. Dinitrogen containing these impurities is passed through a potassium dichromate solution containing dilute sulphuric acid. The impurities are absorbed by the potassium dichromate solution and the pure dinitrogen gas is collected by the downward displacement of water.