Which of the following compounds has the highest melting point?

• A. H2O
• B. C8H18
• C. C12H22O11
• D. Al2(CO3)3

Answer: (D)

Verified step by step guidance

1. Step 1: Identify the types of compounds given in the problem. H2O is a molecular compound with hydrogen bonding, C8H18 (octane) is a nonpolar hydrocarbon with London dispersion forces, C12H22O11 (sucrose) is a molecular compound with hydrogen bonding and some dipole interactions, and Al2(CO3)3 is an ionic compound composed of metal cations and polyatomic anions.
2. Step 2: Understand the nature of intermolecular or ionic forces in each compound. Molecular compounds like H2O, C8H18, and C12H22O11 have intermolecular forces such as hydrogen bonding, dipole-dipole interactions, or London dispersion forces, which are generally weaker than ionic bonds. Ionic compounds like Al2(CO3)3 have strong electrostatic attractions between ions.
3. Step 3: Recall that melting point is largely influenced by the strength of the forces holding the particles together in the solid state. Ionic compounds typically have much higher melting points than molecular compounds because ionic bonds require more energy to break.
4. Step 4: Compare the compounds based on their bonding and intermolecular forces. Since Al2(CO3)3 is ionic, it will have a significantly higher melting point than the molecular compounds H2O, C8H18, and C12H22O11.
5. Step 5: Conclude that the compound with the highest melting point is the ionic compound Al2(CO3)3 due to the strong ionic bonds, which require more energy to overcome compared to the intermolecular forces in the other compounds.