Which of the following solids would be predicted to display the highest melting point?

• A. CO2 (dry ice)
• B. C6H12O6 (glucose)
• C. NaCl (sodium chloride)
• D. I2 (iodine)

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the types of intermolecular or interatomic forces present in each solid. CO2 is a molecular solid held together by London dispersion forces; C6H12O6 (glucose) is a molecular solid with hydrogen bonding; I2 is a molecular solid with London dispersion forces; NaCl is an ionic solid with strong ionic bonds.
2. Step 2: Recall that melting point generally increases with the strength of the forces holding the solid together. Ionic bonds are typically much stronger than hydrogen bonds or dispersion forces.
3. Step 3: Compare the forces: NaCl has strong electrostatic attractions between Na+ and Cl- ions, which require a large amount of energy to break, leading to a high melting point.
4. Step 4: Molecular solids like CO2 and I2 have weaker London dispersion forces, resulting in much lower melting points. Glucose has hydrogen bonding, which is stronger than dispersion forces but still weaker than ionic bonds.
5. Step 5: Conclude that NaCl, due to its ionic bonding, will have the highest melting point among the given solids.