Answer:
Mass of O₂ present in the mixture = 14.7 g
Explanation:
We apply the mole fraction to solve this excersise:
Mole fractio of a gas is:
Moles of X gas / Total moles = Partial pressure of X gas / Total pressure
We determine total pressure:
42 Torr + 159 Torr = 201 Torr
Sum of mole fraction = 1
Mole fraction of O₂ = 159 Torr / 201 Torr → 0.791
1 - Mole fraction of O₂ = Mole fraction of He → 1 - 0.791 = 0.209
We convert the mass of He, in order to determine the moles
1.44 g / 4g/mol = 0.36 moles
Mole fraction He = Moles of He / Total moles
0.36 moles / Total moles = 0.209
0.209 / 0.36 moles = Total moles → 0.580 moles
Mole fraction of O₂ = 0.791 = Moles of O₂ / Total moles
0.791 . 0.580 moles = Moles of O₂ → 0.459 moles
We convert the moles of O₂ to mass → 0.459 mol . 32g / 1mol = 14.7 g
