Answer:
157.29 Torr
Explanation:
This question may be solved by the mole fraction.
Mole fraction → Moles of gas / Total moles = Partial pressure of gas / Total pressure
If the atmosphere is about 21% you assume that the mole fraction is 0.21 so:
0.21 = Partial pressure of gas / Total pressure
0.21 = Partial pressure of gas / 749 Torr
Partial pressure of the gas = 749 Torr . 0.21 → 157.29 Torr
