Question

A balloon contains 0.76 mol N2, 0.18 mol O2, 0.031 mol He and 0.026 mol H2 at 749 mm Hg. What is the partial pressure of O2? a) 20 mm Hg b) 23 mm Hg c) 140 mm Hg d) 570 mm Hg

Answer 1

`"c) 1400 mmHg"`

Explanation:

Mole fraction of `"O"_2`

`chi = ("n"_("O"_2)) / ("n"_("N"_2) + "n"_("O"_2) + "n"_"He" + "n"_("H"_2))`

`chi = "0.18 mol" / ("0.76 mol + 0.18 mol + 0.031 mol + 0.026 mol")`

`chi = 0.1805`

From Dalton’s law of partial pressure

`"p"_("O"_2) = chi × "p"_"total"`

`"p"_("O"_2) = 0.1805 × "749 mmHg" ≈ "140 mmHg"`