Sample Problem 5.6
Calculating the Density of a Gas
PROBLEM:
Calculate the density (in g/L) of carbon dioxide and the number of molecules per liter (a) at STP (0 oC and 1 atm) and (b) at ordinary room conditions (20. oC and 1.00 atm).
PLAN:
SOLUTION:
Density is mass/unit volume; substitute for volume in the ideal gas equation. Since the identity of the gas is known, the molar mass can be determined. Convert mass/L to molecules/L using Avogadro’s number.
d = mass/volume
PV = nRT
V = nRT/P
d
=
d =
= 1.96 g/L
= 2.68 x 1022 molecules CO2/L
(a)
x
x
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