Final answer:
The boiling points of H2S to H2Te increase due to increasing London dispersion forces with size and mass. Water's higher boiling point is due to strong hydrogen bonding, which is much stronger than dispersion forces in heavier hydrides.
Step-by-step explanation:
The trend in boiling points from H2S to H2Te can be attributed to the increasing size and mass of the molecules as we move down group 16 in the periodic table. As the size and mass of the molecules increase, so do the London dispersion forces, which are the exclusive intermolecular forces in nonpolar molecules. This increase in London dispersion forces results in higher boiling points for the heavier hydrides in the group.
However, the boiling point of water (H2O) is anomalously high, compared to other group 16 hydrides, due to the presence of hydrogen bonds. Water has a boiling point of 100°C, which is significantly higher than would be predicted based on its molar mass. Hydrogen bonds are particularly strong dipole-dipole interactions that occur when hydrogen is bonded to highly electronegative atoms such as oxygen, nitrogen, or fluorine. In water, each molecule is capable of forming up to four hydrogen bonds with neighboring molecules, leading to a high degree of intermolecular cohesion and resulting in its much higher boiling point.