Intermolecular forces

Question 1

How do intermolecular forces influence the physical properties of substances?

Answer 1

Intermolecular forces, such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding, significantly influence the physical properties of substances. Stronger intermolecular forces result in higher boiling and melting points, as more energy is required to break the interactions between molecules.

Question 2

What are dipole-dipole forces, and how do they affect the physical properties of polar molecules?

Answer 2

Dipole-dipole forces are attractive forces between polar molecules. they are sufficiently strong to influence many physical properties, including boiling points, melting points, and molecular orientations in solids.

Question 3

What are London dispersion forces, and in which types of molecules do they occur?

Answer 3

Attractions between neutral, nonpolar atoms or molecules arise from the London dispersion forces
(often called van der Waals forces) that exist between all atoms and molecules.

Question 4

State which attractive intermolecular forces are likely dominant in the following substances:(a) F2(s)
(b) HBr(_)
(c) NH4Cl(s)

Answer 4

(a) Molecules of F2 are nonpolar, thus the predominant attractive forces between molecules in F2(s) come from dispersion.
(b) The HBr molecule has a permanent dipole moment. The predominant forces between molecules are dipole–dipole. Dispersion forces will also contribute to associations, especially because Br is a rather heavy atom.
(c) The ammonium ions are attracted to the chloride ions primarily by ion–ion forces.

Question 5

How does hydrogen bond form? And Why are hydrogen bonds stronger than regular dipole-dipole interactions

Answer 5

Such a bond forms when an H atom bonded to an O, N, or F atom (highly electronegative atoms) also interacts with the lone electron pair of another such atom nearby. Hydrogen bonds are stronger than regular dipole-dipole interactions because they involve a hydrogen atom covalently bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine), creating a significant positive charge on the hydrogen. This highly polarized bond allows for a strong attraction between the hydrogen atom and the lone pairs of electrons on another electronegative atom in nearby molecules.