Chapter 4: Problem 114
Indicate the major type of attractive force-(1) ionic bonds, (2) dipole-dipole attractions, (3) hydrogen bonds, (4) dispersion forces-that occurs between particles of the following substances: a. \(\mathrm{CHCl}_{3}\) b. \(\mathrm{H}_{2} \mathrm{O}\) c. \(\mathrm{LiCl}\) d. \(\mathrm{Cl}_{2}\)
Short Answer
Expert verified
a. Dipole-dipole attractions, b. Hydrogen bonds, c. Ionic bonds, d. Dispersion forces.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ionic Bonds
When we talk about ionic bonds, we're looking at a type of chemical bond where atoms transfer electrons to achieve a full outer shell of electrons. This often happens between metals and nonmetals. In the case of \(\text{LiCl}\), or lithium chloride, lithium (a metal) loses an electron to become positively charged, while chlorine (a nonmetal) gains that electron to become negatively charged. These opposite charges attract each other, creating a very strong bond. Ionic bonds are responsible for the high melting and boiling points of ionic compounds, as well as their electrical conductivity when dissolved in water.
Dipole-Dipole Attractions
Dipole-dipole attractions occur between polar molecules, where there is an uneven distribution of charge. A molecule is polar if it has areas of partial positive and negative charge due to differences in electronegativity between the atoms involved. For example, in trichloromethane (\(\text{CHCl}_3\)), the carbon atom forms polar bonds with the chlorine atoms, creating a separation of charges within the molecule. These attractions are not as strong as ionic bonds but are significant enough to influence boiling and melting points. Polar molecules align such that oppositely charged regions come into proximity, creating dipole-dipole interactions.
Hydrogen Bonds
Hydrogen bonds are a special type of dipole-dipole attraction where hydrogen is bonded to highly electronegative atoms like fluorine, oxygen, or nitrogen. In water (\(\text{H}_2\text{O}\)), for instance, the oxygen atom is highly electronegative, pulling electron density away from the hydrogen atoms. This creates a partial positive charge on the hydrogen and a partial negative charge on the oxygen. Because of this, the hydrogen atoms of one water molecule are attracted to the oxygen atoms of nearby water molecules, forming a hydrogen bond. These bonds are stronger than regular dipole-dipole interactions and are the reason for water's unique properties, such as its high boiling point and surface tension.
Dispersion Forces
Dispersion forces, also known as London dispersion forces, are the weakest type of intermolecular force. They occur in all molecules, whether polar or nonpolar, but are the only type of intermolecular force acting in nonpolar molecules like dichlorine (\(\text{Cl}_2\)). These forces arise due to temporary fluctuations in electron distribution, creating a momentary dipole that induces a dipole in a neighboring molecule. Although temporary and weak, dispersion forces increase with the size of the molecule or atom because larger atoms have more electrons that can fluctuate. Dispersion forces are significant in large nonpolar molecules and contribute to the physical properties like melting and boiling points of nonpolar substances.
