Question

NaCl is an ionic solid. The Na+ and Cl− ions in NaCl are bonded through an electrostatic force of attraction commonly known as the ionic bond. Water is a polar solvent. The oxygen atom, being more electronegative, attracts the electron cloud toward itself. As the electron cloud is pulled by the oxygen atom, it carries a partial negative charge, and the hydrogen atoms carry a partial positive charge. This partial separation of charges in the water molecule makes it polar. Predict which intermolecular forces contribute the most to the dissolution of NaCl in water. Check all that apply.

Ion-ion forces
Ion-dipole forces
Dipole-dipole forces
Hydrogen bonding
Suppose that NaCl is added to hexane (C6H14) instead of water. Which of the following intermolecular forces will exist in the system?

Check all that apply.

Ion-dipole force between Na+ ions and a hexane molecule
Ion-ion force between Na+ and Cl− ions
Dipole-dipole force between two hexane molecules
Hydrogen bonding between Na+ ions and a hexane molecule
London dispersion force between two hexane molecules

Answer 1

1. Ion-dipole forces

2.

Ion-ion force between Na⁺ and Cl⁻ ions.

London dispersion force between two hexane molecules.

Step-by-step explanation:

1. Predict which intermolecular forces contribute the most to the dissolution of NaCl in water. Check all that apply.

Na⁺ is attracted to Cl⁻ through ion-ion forces (attraction between solute). Water molecules attract each other through hydrogen bonding (attraction between solvent). For the dissolution to be effective, solute has to interact with the solvent. This happens due to ion-dipole forces, where Na⁺ ions are attracted to the negative part of water (O) and Cl⁻ ions are attracted to the positive part of water (H).

2. Suppose that NaCl is added to hexane (C₆H₁₄) instead of water. Which of the following intermolecular forces will exist in the system?

• Ion-dipole force between Na+ ions and a hexane molecule. FALSE. Hexane is nonpolar.
• Ion-ion force between Na⁺ and Cl⁻ ions. TRUE. This force is present in the solution.

• Dipole-dipole force between two hexane molecules. FALSE. Hexane is nonpolar.

• Hydrogen bonding between Na+ ions and a hexane molecule. FALSE. Hydrogen bonding requires a molecule having H bonded to a very electronegative atom, such as N, O or F.
• London dispersion force between two hexane molecules. TRUE. Nonpolar molecules attract each other through this force, also known as induced dipole-induced dipole force.