Question

co₂(g) and nh₃(g) can be liquefied at 20 °c by compressing them to sufficiently high pressures. a student claims that nh₃(g) can be liquefied at a lower pressure than co₂(g) can be liquefied. which of the following is the best justification for this claim? a at 20 °c, the average speed of nh₃ molecules is greater than that of co₂ molecules because nh₃ molecules have less mass than co₂ molecules have. b co₂ is a nonpolar molecule that has no significant intermolecular forces, whereas nh₃ has strong london dispersion intermolecular forces. c both co₂ and nh₃ are nonpolar molecules that have only london dispersion intermolecular forces, but the larger electron cloud of co₂ molecules causes it to have stronger intermolecular forces. d co₂ is a nonpolar molecule that has london dispersion intermolecular forces

Explanation:

CO₂ is non - polar with only London dispersion forces. NH₃ is polar and has hydrogen bonding (a strong intermolecular force in addition to London dispersion forces). Stronger intermolecular forces in a substance generally mean it can be liquefied at a lower pressure. Option D correctly identifies the nature of CO₂'s intermolecular forces and implies that NH₃, with stronger intermolecular forces, can be liquefied at lower pressure. Option A is about molecular speed which is not related to liquefaction pressure. Option B is incorrect as CO₂ has London dispersion forces and NH₃ has hydrogen bonding and London dispersion forces. Option C is incorrect as NH₃ is polar.

Answer:

D. CO₂ is a nonpolar molecule that has London dispersion intermolecular forces