Which of the following pairs of compounds or ions exhibits an ion-dipole interaction?

• A. NaCl and H2O
• B. CH4 and O2
• C. Cl2 and CCl4
• D. CO2 and NH3

Answer: (A)

Verified step by step guidance

1. Understand what an ion-dipole interaction is: it occurs between an ion (a charged species) and a polar molecule (which has a permanent dipole moment).
2. Identify which species in each pair are ions and which are polar molecules. For example, NaCl dissociates into Na⁺ and Cl⁻ ions in water, and H₂O is a polar molecule with a permanent dipole.
3. Check the other pairs: CH₄ and O₂ are both nonpolar molecules, so they cannot exhibit ion-dipole interactions; Cl₂ and CCl₄ are also nonpolar molecules; CO₂ is nonpolar, and NH₃ is polar but not an ion.
4. Conclude that only the pair containing ions and polar molecules can exhibit ion-dipole interactions, which is NaCl (ions) and H₂O (polar molecule).
5. Remember that ion-dipole interactions are important in processes like the dissolution of ionic compounds in water, where the polar water molecules surround and stabilize the ions.