Arrange these compounds in order of increasing boiling point and explain your reasoning: a. H2S b. H2Se c. H2O.

Verified step by step guidance

1. Identify the intermolecular forces present in each compound: H2S, H2Se, and H2O.
2. Recognize that H2O can form hydrogen bonds, which are stronger than the dipole-dipole interactions present in H2S and H2Se.
3. Note that H2S and H2Se have dipole-dipole interactions, but H2Se has a higher molar mass, leading to stronger London dispersion forces compared to H2S.
4. Arrange the compounds based on the strength of their intermolecular forces: H2O (strongest due to hydrogen bonding), H2Se (stronger London dispersion forces than H2S), and H2S (weakest).
5. Conclude that the order of increasing boiling point is: H2S < H2Se < H2O.

Key Concepts

Intermolecular Forces

Intermolecular forces are the attractions between molecules that influence physical properties like boiling points. The main types include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Stronger intermolecular forces typically result in higher boiling points, as more energy is required to separate the molecules.

Hydrogen Bonding

Hydrogen bonding is a specific type of strong dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine. In the context of the compounds listed, H2O exhibits significant hydrogen bonding due to its O-H bonds, leading to a higher boiling point compared to H2S and H2Se, which do not form hydrogen bonds.

Molecular Weight and Size

Molecular weight and size can also affect boiling points, as larger molecules generally have greater London dispersion forces due to increased electron cloud size. In this case, H2Se has a higher molecular weight than H2S, which contributes to its boiling point being higher than that of H2S, but lower than that of H2O due to the absence of hydrogen bonding.