AFOQT Practice Test

What is the composition of Earth's atmosphere in terms of nitrogen percentage?

1. 21%

2. 50%

3. 78%

4. 90%

The correct answer is: 78%

The correct answer is that nitrogen makes up approximately 78% of Earth's atmosphere. This percentage represents the largest portion of the atmosphere's composition, which is primarily made up of nitrogen and oxygen. The significance of nitrogen in the atmosphere lies in its role in various biological and chemical processes, even though it is relatively inert and does not readily react with other elements under normal conditions. Oxygen, while important for life, comprises about 21% of the atmosphere, and this balance between nitrogen and oxygen is crucial for maintaining a stable environment conducive to living organisms. Other gases, such as carbon dioxide, trace gases, and water vapor, make up a small fraction of the remaining atmosphere. Understanding this composition is key in fields such as environmental science, meteorology, and aeronautics, as it affects everything from weather patterns to flight performance.