Identify the substance in each of the following pairs that...

Identify the substance in each of the following pairs that would have the higher boiling point and explain your choice: a. $\mathrm{NaCl}$ or $\mathrm{HCl}$ b. $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{H}_{2} \mathrm{Se}$ c. $\mathrm{NH}_{3}$ or $\mathrm{PH}_{3}$ d. $\mathrm{F}_{2}$ or $\mathrm{HF}$

Identify the substance in each of the following pairs that would have the higher boiling point and explain your choice:
a. $\mathrm{NaCl}$ or $\mathrm{HCl}$
b. $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{H}_{2} \mathrm{Se}$
c. $\mathrm{NH}_{3}$ or $\mathrm{PH}_{3}$
d. $\mathrm{F}_{2}$ or $\mathrm{HF}$

Key Concepts

Boiling Point

Boiling point is the temperature at which a substance transitions from a liquid to a gas. It largely depends on the strength of the forces that hold the molecules or ions together; stronger attractions result in a higher boiling point because more energy is needed to overcome these forces.

Intermolecular Forces

Intermolecular forces are the attractions between molecules. They include London dispersion forces, dipole-dipole interactions, and hydrogen bonding. The strength and type of these forces significantly influence the boiling point of a substance, with stronger intermolecular forces leading to higher boiling points.

Ionic vs Covalent Bonding

Ionic bonding occurs in compounds composed of ions and involves the electrostatic attraction between positively and negatively charged particles. This type of bonding is typically very strong, often resulting in higher boiling points compared to covalent compounds, where atoms share electrons and exhibit weaker intermolecular attractions.

Hydrogen Bonding

Hydrogen bonding is a specific, strong type of dipole-dipole interaction that occurs when hydrogen is covalently bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine. This bonding dramatically raises the boiling point of a substance by creating strong attractions between molecules.

Molecular Size and Polarizability

Molecular size and polarizability influence the strength of London dispersion forces. Larger molecules with more electrons are more polarizable and can exhibit stronger dispersion forces, which can lead to higher boiling points compared to smaller, less polarizable molecules.

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