Questions and Answers
What is hydrogen bonding?
An intermolecular force between molecules with an -OH/-NH group and molecules with an N/O atom.
Hydrogen bonds are weaker than permanent dipole-dipole forces.
False
What results in the formation of a permanent dipole in a molecule?
A delta positive H and a delta negative O/N due to electronegativity.
How does hydrogen bonding occur in water molecules?
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What are intramolecular forces?
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Which of the following are types of intramolecular forces?
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The three types of intramolecular forces are ionic, covalent, and __________.
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What are intermolecular forces also called?
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What are permanent dipole-permanent dipole forces?
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Ionic bonding is the weakest force among the types of bonding.
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Which type of intermolecular force is the weakest?
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What is hydrogen bonding?
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The bond between hydrogen and an electronegative atom becomes highly __________.
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Which of the following groups can form hydrogen bonds?
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Water can form a maximum of three hydrogen bonds per molecule.
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What are the anomalous properties of water caused by hydrogen bonding?
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Ice floats on water because of ice's __________ density.
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What causes the high enthalpy change of vaporization in water?
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Electronegativity is the ability of an atom to repel electrons.
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What happens to the dipole moment when two atoms in a covalent bond have different electronegativities?
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What type of forces are London dispersion forces?
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How do permanent dipole-permanent dipole forces arise?
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Butane has a higher boiling point than propanone.
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Study Notes
Hydrogen Bonding
- Strongest form of intermolecular bonding, occurs between molecules.
- Requires an electronegative atom (O or N) with a lone pair and an -OH or -NH group.
- When hydrogen is bonded to O or N, the bond is highly polarized, creating a δ+ charged hydrogen capable of forming a bond with another molecule’s lone pair.
- Hydrogen bonds require a 180° angle between -OH/-NH and the hydrogen bond.
- Ammonia can form one hydrogen bond; water can form four hydrogen bonds.
- Hydrogen bonding contributes to water's high melting/boiling points, surface tension, and the anomalous density of ice.
Properties of Water
- High melting and boiling points due to strong hydrogen bonds requiring substantial energy to overcome.
- Water's structure leads to a high enthalpy of vaporization, significantly influenced by hydrogen bonding.
- High surface tension allows water's surface to resist external forces, as surface water molecules are attracted to each other via hydrogen bonds.
- Ice has a lower density than liquid water because of its open hydrogen-bonding network, allowing water to float.
Bond Polarity & Dipole Moments
- Electronegativity defines an atom's ability to attract electrons; it increases across a period and decreases down a group.
- Nonpolar covalent bonds occur when atoms have identical electronegativities; polar covalent bonds exist when there is a difference.
- Polar bonds result in partial charges (δ+ and δ-), creating an asymmetric electron distribution.
- The dipole moment measures bond polarity, indicated by an arrow pointing toward the negative end.
- Molecule polarity depends on the arrangement of polar bonds; some molecules may have polar bonds that cancel each other out and are overall nonpolar.
Van der Waals' Forces
- Weaker than covalent bonds, van der Waals' forces include instantaneous dipole-induced dipole (London dispersion forces) and permanent dipole-permanent dipole forces.
- Instantaneous dipoles arise from shifting electron cloud distributions, inducing dipoles in neighboring molecules.
- Permanent dipoles result from polar covalent bonds with distinct charge distributions.
- Permanent dipole forces are generally stronger than instantaneous dipole forces, impacting boiling points.
Inter & Intramolecular Forces
- Intramolecular forces reside within a molecule, including ionic, covalent, and metallic bonding.
- Ionic bonding involves electrostatic attraction between cations and anions in a lattice formed by electron transfer.
- Covalent bonds occur through sharing of outer electrons, while metallic bonds are due to attractions between metal ions and delocalized electrons.
- Intermolecular forces act between molecules, influencing physical properties such as phase changes and boiling points.### Intramolecular Forces
- Three types of intramolecular forces are ionic, covalent, and metallic bonding.
Intermolecular Forces
- Intermolecular forces, also known as van der Waals' forces, occur between molecules.
- Permanent dipole - permanent dipole forces result from attractive interactions between neighboring molecules that each possess a permanent dipole.
- Hydrogen bonds are a specific kind of permanent dipole - permanent dipole interaction, characterized by strong attractions involving hydrogen atoms.
- Instantaneous dipole - induced dipole (London dispersion) forces arise from temporary dipoles that induce a dipole in neighboring molecules.
Strength of Bonds
- Generally, intramolecular forces are stronger than intermolecular forces.
- Ionic bonding is regarded as the strongest type of force among bonds, while instantaneous dipole - induced dipole forces are the weakest.
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Description
This quiz focuses on the concepts of intermolecular forces, electronegativity, and bond properties in CIE A Level Chemistry. Topics covered include hydrogen bonding, bond polarity, dipole moments, and van der Waals' forces. Test your understanding of the interactions that shape chemical properties.
