Which of the following is the most abundant gas in the Earth's atmosphere?

Question

Examoogle · Accepted Answer

The correct answer is Option C: Nitrogen (~78.08%). Nitrogen is the most abundant gas in the Earth's atmosphere, constituting approximately 78.08% of the air by volume. It acts as a stable, inert diluent for oxygen, preventing rapid combustion and oxidation processes on the Earth's surface.

Step-by-Step Solution & Concepts:
Nitrogen is the most abundant gas in the Earth's atmosphere, constituting approximately 78.08% of the air by volume. It acts as a stable, inert diluent for oxygen, preventing rapid combustion and oxidation processes on the Earth's surface.

Working Principle: The stability of atmospheric nitrogen ($N_2$) is due to the extremely strong triple covalent bond between the two nitrogen atoms. This bond energy is roughly $945 	ext{ kJ/mol}$, making $N_2$ chemically inert under standard temperature and pressure. It does not react readily with other atmospheric components, which allows it to remain at high concentrations.

Key Formulas: $N_2 \equiv N$ — Represents the triple bond in the nitrogen molecule; $78.08\% \approx \frac{4}{5}$ — Approximate fractional composition by volume

Key Points: Nitrogen is a diatomic molecule ($N_2$); It is non-reactive and colorless, odorless, and tasteless; It is a key component of amino acids and nucleic acids in living organisms; Atmospheric pressure at sea level is largely maintained by the mass of nitrogen gas

Advantages: Dilutes oxygen to prevent spontaneous combustion; Essential for protein synthesis in biological life cycles via nitrogen fixation

Disadvantages: High concentrations can cause nitrogen narcosis under high-pressure environments (e.g., deep-sea diving)

Applications: Used in food packaging to prevent oxidation and spoilage; Liquid nitrogen is used as a refrigerant for cryogenic storage

Additional Info: Oxygen ($O_2$) accounts for approximately 20.95% of the atmosphere.. Argon ($Ar$) is the third most abundant gas at 0.93%.. Carbon Dioxide ($CO_2$) is a trace gas at approximately 0.04%.. Nitrogen is biologically fixed into soil by bacteria like Rhizobium.

Answer: C is correct — Nitrogen gas ($N_2$) accounts for about 78% of the Earth's atmosphere by volume.

Exam Tip: Always remember the order of abundance: N > O > Ar > CO2. This is a favorite factual question in competitive exams like UPSC and SSC.

Examoogle · Answer

Option A: Oxygen (~20.95%)

Examoogle · Answer

Option B: Carbon Dioxide (~0.04%)

Examoogle · Answer

Option D: Argon (~0.93%)

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