Natural Science CLEP Prep Practice Exam

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Prepare for the Natural Science CLEP Exam with comprehensive quizzes and multiple choice questions. Each question includes hints and explanations to help you succeed. Ace your exam!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

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What is the most abundant gas in Earth’s atmosphere?

Oxygen
Hydrogen
Nitrogen
Carbon dioxide

The correct answer is: Nitrogen

Despite the fact that oxygen is essential for living beings, it is not the most abundant gas in Earth's atmosphere. Oxygen makes up only about 21% of the Earth's atmosphere. Hydrogen is the lightest gas in the periodic table but it constitutes only about 0.00005% of the Earth's atmosphere. Carbon dioxide, while being important for plant life, only makes up about 0.04% of the Earth's atmosphere. The most abundant gas in Earth's atmosphere is nitrogen, making up about 78% of the Earth's atmosphere. It is colorless and odorless, and is necessary for all living organisms to survive.