Question

How would you explain the partial pressure of oxygen?

Answer 1

In what scenario....?

Explanation:

Atmospheric pressure, `1*atm`, is the sum of the individual partial pressures...

`1*atm=760*mm*Hg=sum(P_(N_2)+P_(O_2)+P_"other gases")`

This is another restatement of old `"Dalton's Law of partial Pressures"`....

For the air we breathe now, `P_(O_2)=160*mm*Hg`...and `P_(N_2)=500*mm*Hg` to a first approx...

For the relation between partial pressure and mole fraction, see here.