Final answer:
The correct order of the compounds by increasing boiling points is N₂ < CS₂ < H₂O < KCl (option a). This order is based on the strength of the intermolecular forces present in each compound, from the weakest (London dispersion forces in N₂) to the strongest (ionic bonds in KCl).
Step-by-step explanation:
The compounds listed correctly in order of increasing boiling points are N₂ < CS₂ < H₂O < KCl, which corresponds to option (a). To understand the rationale behind this, let's consider the type of intermolecular forces present in each compound:
N₂ (Nitrogen) is a nonpolar diatomic molecule and thus has weak London dispersion forces as the dominant intermolecular force. CS₂ (Carbon Disulfide) is a slightly larger nonpolar molecule than N₂, which means it will have stronger dispersion forces and a higher boiling point.
H₂O (Water) has strong hydrogen bonding in addition to London dispersion and dipole-dipole forces, which accounts for its high boiling point relative to its molecular weight. KCl (Potassium Chloride) is an ionic compound, and the strong ionic bonds give it a very high boiling point.
Therefore, considering intermolecular forces and the strength of these attractions, it explains why the compounds are ordered as they are for increasing boiling points.