What percentage of oxygen is present in dry air?

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards
From $24.99Unlock all

Study for the IGCSE Edexcel Chemistry Test. Access flashcards and multiple choice questions with hints and explanations. Get ready for your exam!

Multiple Choice

What percentage of oxygen is present in dry air?

Explanation:
Oxygen makes up about 21% of dry air by volume, meaning roughly one-fifth of the gas molecules in a sample of dry air are oxygen. The rest is mainly nitrogen, which is about 78%, with small amounts of other gases like argon (around 0.9%) and carbon dioxide (about 0.04%). The term “dry air” means there’s no water vapour, so these percentages reflect the composition by molecules in the absence of humidity. Because of this, the oxygen fraction is best described as ~21%, not the other numbers shown.

Oxygen makes up about 21% of dry air by volume, meaning roughly one-fifth of the gas molecules in a sample of dry air are oxygen. The rest is mainly nitrogen, which is about 78%, with small amounts of other gases like argon (around 0.9%) and carbon dioxide (about 0.04%). The term “dry air” means there’s no water vapour, so these percentages reflect the composition by molecules in the absence of humidity. Because of this, the oxygen fraction is best described as ~21%, not the other numbers shown.

More Multiple Choice Questions
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy