The mole fraction of oxygen molecules in dry air is 0.2095.

Daltons Law:
Po2/90=.2095

Po2=18.8 kPa

This is a follow up from yesterday, how did you get the mole fraction? I don't get it

1 answer

Bob Pursley answered your question yesterday. The mole fraction of gases is the percent; i.e., oxygen is about 21% oxygen so the mole fraction is 0.21.
pO2 = XO2 x Ptotal