Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What is the most abundant gas in the atmosphere?

1. Oxygen

2. Carbon dioxide

3. Nitrogen

4. Argon

The correct answer is: Nitrogen

The most abundant gas in the atmosphere is nitrogen, which comprises about 78% of the Earth's atmosphere by volume. This significant presence plays a crucial role in various processes, including the nitrogen cycle, which is essential for life as it helps in the formation of amino acids and proteins necessary for all living organisms. Understanding the composition of the atmosphere is fundamental in fields such as environmental science and biology, as it helps explain phenomena such as air quality, climate change, and the biodiversity of ecosystems. While other gases like oxygen are vital for respiration and combustion, they are present in much smaller amounts, constituting about 21% of the atmosphere. Carbon dioxide and argon are present in even lesser concentrations, with carbon dioxide being important for photosynthesis and global warming discussions. Thus, nitrogen's dominance highlights its essential role in supporting life and maintaining atmospheric balance.