A 3.0 mol sample of an unknown gas confined to 1.0 L at 200 K exerts a measured…
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A 3.0 mol sample of an unknown gas confined to 1.0 L at 200 K exerts a measured pressure of 28 bar. Under the same conditions, the pressure calculated using the ideal-gas law is 49 bar. Which of the following best explains the large deviation from ideal behavior?
(a) Because the gas has a very large molar mass, its root-mean-square speed is lower than that assumed for an ideal gas, so fewer and weaker collisions produce the lower pressure.
(b) Repulsive forces arising from the finite molecular volume reduce the space in which the gas can move, thereby lowering the pressure relative to the ideal-gas prediction.
(c) Strong intermolecular attractions greatly reduce the frequency and momentum of wall collisions, indicating a large value of the attraction parameter.
(d) The temperature is so low that the kinetic energy of the molecules is insufficient to maintain ideal behavior, so their slower motion alone accounts for the reduced pressure.