Chapter 12, Problem 12.91QP

Interpretation Introduction

Interpretation:

The false one from the following statements has to be identified –

1. (a) Dipole-dipole interactions between molecules are greatest if the molecules possess only temporary dipole moments.

1. (b) All compounds containing hydrogen atoms can participate in hydrogen-bond formation.

1. (c) Dispersion forces exist between all atoms, molecules, and ions.

Concept Introduction:

• Intermolecular forces are the force of attraction between the molecules in a compound.
• The physical state of a substance depends on the strength of the intermolecular forces present in the molecules of that substance.
• Very strong intermolecular forces bind the molecules together tightly and form “solids”. The molecules are held together strongly in solids that they hardly move from their respective position.
• Liquid molecules have relatively low strength of intermolecular forces between them. Thus they move freely and because of this liquids do “flow”.
• Gaseous substances have weakest intermolecular forces between them. Usually intermolecular forces are considered negligible in case of gaseous compounds. Gaseous molecules exhibit very rapid and random movement.
• The classification of intermolecular forces can be summarized as follows –

• There are three types of intermolecular forces - London dispersion forces, dipole-dipole forces and hydrogen bonding.  These forces are collectively known as Van der Waals forces.
• London dispersion forces exist in non-polar covalent compounds consists of temporary or instant dipoles and almost all type of compounds.
• Dipole-dipole forces present in polar covalent compounds consists of permanent dipoles.
• Hydrogen bonding is formed in polar covalent compounds containing direct bond between Hydrogen and other high electronegativity like Fluorine, Oxygen or Nitrogen. It is relatively the strongest one.