Which of the following in each pair is likely to be more soluble in water: (c) HCl or ethyl chloride (CH₃CH₂Cl)? Explain in each case.

Key Concepts

Polarity and Solubility

Polarity refers to the distribution of electrical charge over the atoms in a molecule. Polar molecules, which have a significant difference in electronegativity between their atoms, tend to dissolve well in polar solvents like water. This is due to the 'like dissolves like' principle, where polar solutes are more soluble in polar solvents, while nonpolar solutes are better dissolved in nonpolar solvents.

Hydrogen Bonding

Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine. In the case of HCl, the molecule can form hydrogen bonds with water, enhancing its solubility. Ethyl chloride, being a nonpolar molecule, lacks the ability to form such interactions, making it less soluble in water.

Molecular Structure and Functional Groups

The molecular structure and functional groups of a compound significantly influence its solubility. HCl is a simple diatomic molecule that ionizes in water to form H⁺ and Cl⁻ ions, increasing its solubility. In contrast, ethyl chloride has a larger hydrocarbon structure with a chlorine atom, which does not ionize and is less compatible with water, leading to lower solubility.