Which of the following substances is the least fluid due to strong intermolecular forces?

• A. H2O (water, liquid)
• B. NaCl (sodium chloride, solid)
• C. CH3OH (methanol, liquid)
• D. CO2 (carbon dioxide, gas)

Answer: (B)

Verified step by step guidance

1. Understand that fluidity refers to how easily a substance flows, which is influenced by the strength of its intermolecular forces. Stronger intermolecular forces generally mean less fluidity.
2. Identify the physical state of each substance at room temperature: H2O and CH3OH are liquids, CO2 is a gas, and NaCl is a solid. Solids typically have very strong intermolecular (or ionic) forces, making them the least fluid.
3. Recall the types of intermolecular forces present: H2O and CH3OH have hydrogen bonding, CO2 has weak London dispersion forces, and NaCl is an ionic compound with strong ionic bonds.
4. Recognize that ionic bonds in NaCl are much stronger than the hydrogen bonds in H2O and CH3OH or the dispersion forces in CO2, resulting in NaCl being a solid with very low fluidity.
5. Conclude that NaCl is the least fluid substance among the options due to its strong ionic bonds, which hold its ions rigidly in a solid lattice.