To determine which substance most likely has the highest boiling point among the given options: calcium chloride (CaCl₂), methanol (CH₃OH), and carbon tetrachloride (CCl₄), we need to analyze the types of compounds and the nature of bonding in each.
1. Calcium Chloride (CaCl₂):
- Type of Compound: Ionic
- Nature of Bonding: Ionic compounds consist of a lattice of positively charged cations and negatively charged anions. The ionic bonds between the oppositely charged ions are very strong, requiring a significant amount of energy to break.
- Boiling Point: Ionic compounds generally have very high boiling points due to the strong electrostatic forces between the ions.
2. Methanol (CH₃OH):
- Type of Compound: Polar covalent
- Nature of Bonding: Methanol has polar covalent bonds due to the difference in electronegativity between the carbon, hydrogen, and oxygen atoms. Additionally, methanol exhibits hydrogen bonding due to the -OH group.
- Boiling Point: Hydrogen bonds are relatively strong compared to other intermolecular forces like Van der Waals forces, but they are still weaker than ionic bonds. Therefore, methanol has a moderately high boiling point but not as high as ionic compounds.
3. Carbon Tetrachloride (CCl₄):
- Type of Compound: Nonpolar covalent
- Nature of Bonding: Carbon tetrachloride is a nonpolar molecule with covalent bonds where the electrons are shared equally. The predominant intermolecular forces are London dispersion forces (Van der Waals forces), which are the weakest type.
- Boiling Point: Nonpolar covalent compounds have relatively low boiling points because the intermolecular forces are weak.
Given the analysis of the types of bonding and the strengths of these interactions, the substance with the highest boiling point is:
Calcium chloride (CaCl₂)
This conclusion is based on the fact that ionic bonds in calcium chloride require significantly more energy to break compared to the hydrogen bonds in methanol and the London dispersion forces in carbon tetrachloride.
