What percentage of oxygen is present in the atmosphere?

Study for the Kentucky Surface Mine Exam. Review with flashcards and multiple choice questions, each question includes hints and explanations. Prepare effectively for your test!

Multiple Choice

What percentage of oxygen is present in the atmosphere?

Explanation:
Oxygen is the second most abundant gas in the atmosphere, making up about one-fifth of the air by volume. In dry air, the typical value used is around 21 percent O2 (about 20.9% by volume). That fraction is what safety calculations and ventilation plans in mining rely on because percentages are measured as volumes (moles) of gases in the air. So the correct value to remember is about 21 percent. The other numbers would imply a noticeably different atmospheric composition and are not the standard figure for breathable air.

Oxygen is the second most abundant gas in the atmosphere, making up about one-fifth of the air by volume. In dry air, the typical value used is around 21 percent O2 (about 20.9% by volume). That fraction is what safety calculations and ventilation plans in mining rely on because percentages are measured as volumes (moles) of gases in the air. So the correct value to remember is about 21 percent. The other numbers would imply a noticeably different atmospheric composition and are not the standard figure for breathable air.

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