Final answer:
The boiling point of AsH3 is lower than that of NH3 due to weaker intermolecular forces.
Step-by-step explanation:
The boiling point is determined by the strength of intermolecular forces (IMFs) between molecules. The higher the IMFs, the higher the boiling point. In the case of AsH3 and NH3, the boiling point of AsH3 is lower because it has weaker IMFs compared to NH3.
The difference in boiling points can be attributed to the presence of hydrogen bonding in NH3. Hydrogen bonding is a strong IMF that occurs when a hydrogen atom that is covalently bonded to a highly electronegative atom (such as nitrogen) interacts with another highly electronegative atom.
Since AsH3 does not have hydrogen bonding, its IMFs are weaker compared to NH3, resulting in a lower boiling point.