Answer:
The difference in boiling points between HF and HI can be rationalized based on the presence of hydrogen bonding in HF, which leads to stronger intermolecular forces and a higher boiling point.
Step-by-step explanation:
The difference in boiling points between HF (hydrogen fluoride) and HI (hydrogen iodide) can be rationalized based on the strength of the intermolecular forces in each substance. Here's a step-by-step explanation:
1. Intermolecular forces: The boiling point of a substance is determined by the strength of the intermolecular forces holding its molecules together. The stronger the intermolecular forces, the higher the boiling point.
2. Hydrogen bonding: Both HF and HI are polar molecules, meaning they have a positive and a negative end. However, HF can form hydrogen bonds, while HI cannot.
3. Hydrogen bonding in HF: Hydrogen bonding occurs when a hydrogen atom is bonded to a highly electronegative atom, such as fluorine (F) in this case. The fluorine atom attracts the bonded electron pair towards itself, creating a partial positive charge on the hydrogen atom. This partial positive charge can then interact with the lone pairs of electrons on nearby fluorine atoms, leading to stronger intermolecular forces.
4. Weaker intermolecular forces in HI: In contrast, hydrogen iodide (HI) does not exhibit hydrogen bonding because iodine (I) is less electronegative than fluorine. As a result, the intermolecular forces in HI are weaker than those in HF.
5. Boiling points: The stronger the intermolecular forces, the higher the boiling point. Since HF has stronger intermolecular forces due to hydrogen bonding, it requires more energy to break these bonds and reach the boiling point. Therefore, HF has a higher boiling point of 20°C compared to HI, which has a lower boiling point of -100°C.