Question

Consider the compounds \(\mathrm{Cl}_{2}, \mathrm{HCl}, \mathrm{F}_{2}, \mathrm{NaF}\), and \(\mathrm{HF}\). Which compound has a boiling point closest to that of argon? Explain.

Short answer

The compound with the boiling point closest to that of argon (-185.8 °C) is \(\mathrm{F}_{2}\) with a boiling point of -188.11 °C. This is because both argon and \(\mathrm{F}_{2}\) are nonpolar atoms with weak van der Waals forces in argon and covalent bonding in diatomic F2 molecules. The nonpolar nature of both substances results in their boiling points being similar. The other given compounds have different types of bonding, which leads to significantly different boiling points compared to argon.

Step-by-step solution

Determine the category of Argon

Argon is an inert, monoatomic noble gas that has a boiling point of -185.8 °C. It does not form molecules or compounds since it has a completely filled electron shell. In the gas phase, argon consists of single Ar atoms interacting with one another through weak van der Waals forces.

Analyze types of bonding for given compounds

1. \(\mathrm{Cl}_{2}\) - This is a diatomic molecule in which two chlorine atoms are bonded together through a covalent bond. Cl has a boiling point of -34.6 °C. 2. \(\mathrm{HCl}\) - Hydrochloric acid is a polar covalent molecule formed between hydrogen and chlorine atoms. HCl's boiling point is -85.05 °C. 3. \(\mathrm{F}_{2}\) - Fluorine is similar to chlorine in that it is a diatomic molecule with covalent bonding between two F atoms. The boiling point of F2 is -188.11 °C. 4. \(\mathrm{NaF}\) - Sodium fluoride is an ionic compound formed between sodium (Na) and fluorine (F) atoms. NaF has a boiling point of 1681 °C. 5. \(\mathrm{HF}\) - Hydrogen fluoride is a polar covalent molecule formed between hydrogen (H) and fluorine (F) atoms. The boiling point of HF is 19.54 °C.

Compare boiling points of compounds with argon

We can now compare the boiling points of the given compounds with that of argon: - Argon (-185.8 °C) - \(\mathrm{Cl}_{2}\) (-34.6 °C) - \(\mathrm{HCl}\) (-85.05 °C) - \(\mathrm{F}_{2}\) (-188.11 °C) - \(\mathrm{NaF}\) (1681 °C) - \(\mathrm{HF}\) (19.54 °C) Among these compounds, the boiling point of F2 is closest to the boiling point of argon (-185.8 °C). Therefore, \(\mathrm{F}_{2}\) has a boiling point closest to that of argon.

Explain the result

The compound with the boiling point closest to that of argon is \(\mathrm{F}_{2}\). This is because both argon and \(\mathrm{F}_{2}\) are nonpolar atoms. Argon exists as single Ar atoms in the gas phase with weak van der Waals forces, while F2 exists as diatomic molecules with covalent bonding. The nonpolar nature of both substances results in their boiling points being similar. Other compounds, such as \(\mathrm{NaF}\), have much higher boiling points because of the strong ionic bonding, while polar covalent molecules like \(\mathrm{HCl}\) and \(\mathrm{HF}\) have moderately different boiling points due to dipole-dipole interactions.