The table lists experimentally determined constants for two gases.
Gas a (L2·bar·mol−2) b (L·mol−1)
X 2.3 0.042
Y 0.9 0.092
One mole of each gas is compressed separately to 1.0 L at 300 K. Based on the data, which gas will exert the lower pressure than predicted by the ideal-gas law, and which intermolecular factor is primarily responsible?
(a) Gas Y will exert the lower pressure because its larger excluded volume (larger b) reduces the space available for motion.
(b) Gas Y will exert the lower pressure because, according to the table, it has the larger a value indicating stronger attractions.
(c) Gas X will exert the lower pressure because stronger intermolecular attractions (larger a) dominate.
(d) Gas X will exert the lower pressure because its smaller excluded volume (smaller b) leads to a lower collision frequency.