Which substance most likely has the highest boiling point?

A. Calcium chloride [tex]$\left( \text{CaCl}_2 \right)$[/tex], an ionic compound
B. Methanol [tex]$\left( \text{CH}_3\text{OH} \right)$[/tex], a polar covalent compound
C. Carbon tetrachloride [tex]$\left( \text{CCl}_4 \right)$[/tex], a nonpolar covalent compound



Answer :

To determine which substance most likely has the highest boiling point, we should consider the nature of the bonds within each substance and the type of intermolecular forces they exhibit. Substances with stronger intermolecular forces generally have higher boiling points.

1. Calcium chloride [tex]\(\left( CaCl_2 \right)\)[/tex]:
- Type of compound: Ionic compound.
- Intermolecular forces: Ionic compounds are held together by electrostatic forces between oppositely charged ions. These ionic bonds are very strong.
- Impact on boiling point: Due to the strong ionic bonds, calcium chloride has a very high boiling point.

2. Methanol [tex]\(\left( CH_3OH \right)\)[/tex]:
- Type of compound: Polar covalent compound.
- Intermolecular forces: Methanol molecules exhibit hydrogen bonding due to the presence of a hydroxyl group [tex]\(\left( -OH \right)\)[/tex]. Hydrogen bonds are significant, but weaker compared to ionic bonds.
- Impact on boiling point: Methanol has a moderate boiling point, higher than typical nonpolar covalent compounds, but lower than ionic compounds.

3. Carbon tetrachloride [tex]\(\left( CCl_4 \right)\)[/tex]:
- Type of compound: Nonpolar covalent compound.
- Intermolecular forces: Nonpolar covalent compounds are held together primarily by London dispersion forces (Van der Waals forces), which are relatively weak.
- Impact on boiling point: Due to these weak forces, carbon tetrachloride has a relatively low boiling point.

Comparing these substances, ionic bonds present in calcium chloride are the strongest among the intermolecular forces considered here, resulting in the highest boiling point.

Thus, the substance most likely to have the highest boiling point is:
Calcium chloride (CaCl_2).