The freezing point of helium is -270°C.The freezing point of xenon is -112°C.Both of these are in the noble gas family.Which of the following statements is supported by these data?
A)Helium and xenon form highly polar molecules.
B)As the molecular weight of the noble gas increases,the freezing point decreases.
C)The London dispersion forces between the helium molecules are greater than the London dispersion between the xenon molecules.
D)The London dispersion forces between the helium molecules are less than the London dispersion forces between the xenon molecules.
E)None of these.

Question

Quizplus · Accepted Answer

The freezing point of a substance is directly related to the strength of the intermolecular forces holding its molecules together. In the case of noble gases, the only intermolecular force present is the London dispersion force, which is proportional to the size and polarizability of the atom or molecule. As the atomic size and weight increase from helium to xenon, the strength of the London dispersion force increases, resulting in a higher freezing point for xenon than helium. Therefore, the correct choice is D, indicating that the London dispersion forces between the helium molecules are less than those between the xenon molecules.

The Freezing Point of Helium Is -270°C