CIE A Level Chemistry 3.6
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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?

<p>Between the oxygen lone pair of one water molecule and the δ+ hydrogen atoms of another water molecule.</p> Signup and view all the answers

What are intramolecular forces?

<p>Forces within a molecule.</p> Signup and view all the answers

Which of the following are types of intramolecular forces?

<p>Metallic bonding</p> Signup and view all the answers

The three types of intramolecular forces are ionic, covalent, and __________.

<p>metallic</p> Signup and view all the answers

What are intermolecular forces also called?

<p>Van der Waals' forces.</p> Signup and view all the answers

What are permanent dipole-permanent dipole forces?

<p>Attractive forces between two neighboring molecules with permanent dipoles.</p> Signup and view all the answers

Ionic bonding is the weakest force among the types of bonding.

<p>False</p> Signup and view all the answers

Which type of intermolecular force is the weakest?

<p>Instantaneous dipole - induced dipole (London dispersion) forces.</p> Signup and view all the answers

What is hydrogen bonding?

<p>The strongest form of intermolecular bonding.</p> Signup and view all the answers

The bond between hydrogen and an electronegative atom becomes highly __________.

<p>polarised</p> Signup and view all the answers

Which of the following groups can form hydrogen bonds?

<p>An -NH group</p> Signup and view all the answers

Water can form a maximum of three hydrogen bonds per molecule.

<p>False</p> Signup and view all the answers

What are the anomalous properties of water caused by hydrogen bonding?

<p>High melting and boiling points, high surface tension, and anomalous density of ice compared to water.</p> Signup and view all the answers

Ice floats on water because of ice's __________ density.

<p>lower</p> Signup and view all the answers

What causes the high enthalpy change of vaporization in water?

<p>The presence of strong hydrogen bonds.</p> Signup and view all the answers

Electronegativity is the ability of an atom to repel electrons.

<p>False</p> Signup and view all the answers

What happens to the dipole moment when two atoms in a covalent bond have different electronegativities?

<p>The electrons are drawn towards the more electronegative atom, creating a polar bond.</p> Signup and view all the answers

What type of forces are London dispersion forces?

<p>Temporary dipole-induced dipole forces</p> Signup and view all the answers

How do permanent dipole-permanent dipole forces arise?

<p>They arise between polar molecules with permanent dipoles.</p> Signup and view all the answers

Butane has a higher boiling point than propanone.

<p>False</p> Signup and view all the answers

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.

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