Question

Together, nitrogen (n2) and oxygen (o2) by volume account for _____% of the gases composing the dry air in the lower atmosphere (below an altitude of 80 km).

Answer 1

Together, nitrogen (N₂) and oxygen (O₂) by volume account for 99,03% of the gases composing the dry air in the lower atmosphere.
Volume of nitrogen in air is 78,08%.
Volume of oxygen in air is 20,95%.
Together: 78,08% + 20,95% = 99,03%.
This gases can be separated by fractional distillation of liquefied air.