Question 27

N2 is found in the atmosphere in the greatest concentration.

Nitrogen (N2) constitutes approximately 78% of the Earth's atmosphere, making it the most abundant gas present. This high concentration significantly exceeds that of other atmospheric gases.

A) O2

Oxygen (O2) is present in the atmosphere at about 21%, making it the second most abundant gas. While essential for life, its concentration is far lower than that of nitrogen, thus it cannot be the correct answer.

B) N2

Nitrogen (N2) is the correct answer, as it is the most prevalent gas in the atmosphere, accounting for nearly 78% of its composition. This significant concentration establishes nitrogen as the primary component of air.

C) H2

Hydrogen (H2) is found in the atmosphere only in trace amounts, making up a very small fraction of the total gases. Its low concentration disqualifies it from being the answer to the question.

D) CO2

Carbon dioxide (CO2) is present in the atmosphere at approximately 0.04%, which is a minuscule concentration compared to nitrogen. Therefore, it is not the correct choice in this context.

Conclusion

N2 is definitively the most abundant gas in the atmosphere, comprising a substantial majority of its composition, while all other options—O2, H2, and CO2—are present in much lower concentrations. This fundamental understanding of atmospheric composition clarifies why nitrogen is the correct answer and underscores the minimal presence of the other gases listed.