Question

A. What mass of carbon dioxide is present in 1.00 m3 of dry air at a temperature of 15 ∘C and a pressure of 703 torr ?

Express your answer with the appropriate units.

B.

Calculate the mass percentage of oxygen in dry air.

Express your answer with the appropriate units.

Answer 1

A)
P =   703 torr = 0.925 atm
V = 1 m3 = 1000L
T = 15 ∘C = 288K
R = 0.0821 L atm mol^-1K^-1

PV = nRT; n =PV/RT
n = (0.925 atm x 1000L)/ (0.0821 L atm mol^-1K^-1 x 288K) = 39.12 mol
Molar mass of carbon dioxide =44 g/mol
mass of carbon dioxide = Moles x Molar mass = 44 g/mol x 39.12 mol = 1721.28 g
Mass of carbon dioxide = 1721.3 g

B)
Dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.
the mass percentage of oxygen in dry air is 21% (approx.)