Approximately what percent of the atmosphere is oxygen?

Study for the Paramedic Aandamp;P Exam. Engage with flashcards and multiple choice questions, complete with hints and explanations. Prepare effectively for your exam!

Multiple Choice

Approximately what percent of the atmosphere is oxygen?

Think of the atmosphere in terms of how much of it is made up by each gas by volume. Oxygen is a large part, but not the majority—it's about one-fifth of the air, roughly 21 percent. That’s why the correct answer is about 21%. The rest is mainly nitrogen (about 78%), with small amounts of other gases. Water vapor varies with humidity, but it doesn’t change the general rule that oxygen is around one-fifth of the mixture. The other options don’t fit: 78% would be nitrogen, 0.03% is far too little for oxygen (that would be closer to trace gases like CO2 at times), and 100% would be pure oxygen, not what the atmosphere contains.

Think of the atmosphere in terms of how much of it is made up by each gas by volume. Oxygen is a large part, but not the majority—it's about one-fifth of the air, roughly 21 percent. That’s why the correct answer is about 21%. The rest is mainly nitrogen (about 78%), with small amounts of other gases. Water vapor varies with humidity, but it doesn’t change the general rule that oxygen is around one-fifth of the mixture. The other options don’t fit: 78% would be nitrogen, 0.03% is far too little for oxygen (that would be closer to trace gases like CO2 at times), and 100% would be pure oxygen, not what the atmosphere contains.

More practice questions