alleryStart learning →Earth's atmosphere is roughly what composition by the two main gases?
AAbout 78% oxygen and 21% nitrogen
BAbout 78% nitrogen and 21% oxygen
CAbout 21% nitrogen and 78% argon
DAbout 50% nitrogen and 50% oxygen
Answer & Solution
Correct answer: B. About 78% nitrogen and 21% oxygen
1. Air is a mixture, and two gases dominate it.
2. Nitrogen makes up roughly 78.1 percent of the atmosphere.
3. Oxygen makes up roughly 21.0 percent, leaving under one percent for everything else.
4. Swapping the two figures is the standard slip, so check which gas carries the larger share before answering.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.1 Gas Pressure_
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