Final answer:
True, NH3 does not follow the trend of boiling points with PH3, AsH3, and SbH3 due to the strong hydrogen bonding in NH3, which increases its boiling point beyond the trend observed for heavier hydrides.
Step-by-step explanation:
The statement that NH3 does not follow the trend of boiling points with PH3, AsH3, and SbH3 is true. In the case of NH3, its boiling point is significantly higher than what would be predicted based on the trend followed by the rest of the group 15 hydrides. The reason behind this discrepancy is the presence of hydrogen bonding in NH3, which is a strong intermolecular force that raises the boiling points of molecules such as NH3, H2O, and HF, beyond the trend observed for heavier hydrides in their respective groups. For heavier hydrides such as PH3, AsH3, and SbH3, the primary intermolecular forces are dispersion forces, which increase with increasing molecular size, leading to a gradual increase in boiling points down the group. However, the effect of hydrogen bonding in NH3 is much stronger than dispersion forces, resulting in a higher boiling point than would be otherwise expected.