Question

What is the partial pressure of oxygen?

Answer 1

In the atmosphere?

Explanation:

At sea level, since dioxygen 21% of the the atmosphere, the partial pressure of dioxygen is `0.21xx1*atm=0.21*atm`. What is the partial pressure of dinitrogen if dinitrogen constitutes 79% of the atmosphere?

Note that, as here and as always, the total pressure is the sum of the individual partial pressures: here `1*atm=(0.21+0.79)*atm` as required.