The compounds can be ranked in order of decreasing boiling point based on the strength of their intermolecular forces. Potassium fluoride (KF) has the highest boiling point due to strong ionic bonds, followed by iodomethane (CH₃I) with dipole-dipole interactions, and acetylene (C₂H₂) with the weakest London dispersion forces.
To rank the compounds in order of decreasing boiling point, we need to consider the intermolecular forces present in each compound. The strength of these forces determines the boiling point, with stronger forces requiring more energy to break and thus resulting in a higher boiling point.
Let's analyze the compounds and their intermolecular forces:
1. Potassium fluoride (KF): KF is an ionic compound composed of potassium cations (K+) and fluoride anions (F-). Ionic compounds have strong electrostatic attractions between ions called ion-ion interactions or ionic bonds. These forces are relatively strong and require a significant amount of energy to break, resulting in a high boiling point.
2. Iodomethane (CH₃I): Iodomethane is a polar molecule. It has a slightly positive carbon atom and a slightly negative iodine atom. The polar nature of the molecule leads to dipole-dipole interactions between neighboring iodomethane molecules. These intermolecular forces are weaker than ionic bonds but stronger than the forces present in nonpolar molecules.
3. Acetylene (C₂H₂): Acetylene is a nonpolar molecule with a linear structure. It consists of two carbon atoms bonded by a triple bond and two hydrogen atoms. Nonpolar molecules, like acetylene, have weak intermolecular forces known as London dispersion forces or van der Waals forces. These forces are the weakest among the intermolecular forces.
Based on the strength of intermolecular forces:
1. Potassium fluoride (KF) - highest boiling point
2. Iodomethane (CH₃I)
3. Acetylene (C₂H₂) - lowest boiling point