Question

The types of attractive forces between a polar molecule and a non-polar molecule are (a) dipole-dipole forces (b) hydrogen bonds (c) dipole-induced dipole forces (d) dispersion forces.

Short answer

The type of attractive force between a polar molecule and a non-polar molecule is (c) dipole-induced dipole forces.

Step-by-step solution

Understand the Types of Intermolecular Forces

The first step is to understand the different types of intermolecular forces that can exist between molecules. These are generally categorized as ionic, hydrogen bonding, dipole-dipole, dipole-induced dipole, and dispersion (or London) forces.

Define the Types of Molecules Involved

Next, define the two types of molecules mentioned: a polar molecule has a permanent dipole due to an uneven distribution of electrons, while a non-polar molecule has an even distribution of electrons and no permanent dipole.

Identify the Applicable Intermolecular Force

Since we have a polar molecule and a non-polar molecule, the intermolecular force in question cannot be dipole-dipole, hydrogen bonding, or exclusively dispersion forces. Dipole-dipole forces and hydrogen bonds require both interacting molecules to have a permanent dipole, while dispersion forces are typically the only force between non-polar molecules. However, the polar molecule can induce a dipole in the non-polar molecule, leading to dipole-induced dipole forces.

Key concepts

Dipole-Induced Dipole Forces

Intermolecular forces play a pivotal role in determining the physical properties of substances. Among these forces are dipole-induced dipole forces, also known as London dispersion forces. These occur when a molecule with a permanent dipole, such as water (H₂O), induces a dipole moment in a neighboring non-polar molecule, like oxygen (O₂). This is possible because the electric field of the polar molecule can cause a distortion in the electron cloud of the non-polar molecule, leading to a temporary dipole.

Consider, for instance, the interaction between nitrogen monoxide (NO), a polar molecule, and nitrogen (N₂), which is nonpolar. The electron-rich area of NO interacts with the electron cloud of N₂, briefly polarizing it and inducing a dipole. This temporary interaction is generally weaker compared to permanent dipole-dipole interactions but plays a significant role in the behavior of mixed substances. Understanding this concept can help explain varying boiling points and solubilities of different molecular mixtures.

Polar and Non-Polar Molecules

The distinction between polar and non-polar molecules is crucial in chemistry and has a profound impact on how molecules interact with one another. Polar molecules have a partial positive and negative charge (called dipoles) due to an uneven distribution of electrons within the molecule, which often results from the molecule having atoms with differing electronegativity. Common examples include water (H₂O) and hydrochloric acid (HCl).

On the other hand, non-polar molecules have a uniform distribution of electronic charge, usually because they consist of atoms of similar electronegativity or because they have a symmetrical geometric structure that cancels out any individual dipole moments. Molecules like methane (CH₄) and carbon dioxide (CO₂) fall into this category. By understanding whether a molecule is polar or non-polar, one can predict how it will interact with other molecules, influencing properties like state of matter, melting and boiling points, and even biological function.

Types of Intermolecular Forces

In the realm of molecular interactions, recognizing the types of intermolecular forces at play is crucial. These forces are essentially the glue that holds molecules together in different states of matter. They include ionic bonds, hydrogen bonds, dipole-dipole interactions, dipole-induced dipole forces, and dispersion (or London) forces.

Ionic bonds are strong electrostatic attractions between oppositely charged ions. Hydrogen bonds, which are stronger than Van der Waals forces but weaker than ionic bonds, occur when a hydrogen atom bonded to a highly electronegative atom is attracted to an electronegative atom in another molecule. Dipole-dipole interactions happen between molecules that have permanent dipoles, affecting substances like HCl. London dispersion forces, the weakest intermolecular force, are present in all molecules and result from temporary fluctuations in electron density. These various forces dictate the physical properties of compounds and their interactions with each other, making them fundamental concepts in understanding chemical behavior.