Answer:
Mole fraction O₂ = 452 mmHg/ 780mmHg → 0.579
Step-by-step explanation:
Mole fraction is defined as the quotient between Partial Pressure of a gas, in a mixture and the Total Pressure from the mixture
Partial pressure of a gas/ Total pressure
Mole fraction O₂ = 452 mmHg/ 780mmHg → 0.579
Be careful, because mole fraction doesn't have units