Chapter 8.4, 9.1, 9.2

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Chapter 8.4, 9.1, 9.2 Intermolecular Forces
Continued and The Nature of Solutions

• CHM1111 Section 04
• Instructor Dr. Jules Carlson
• Class Time M/W/F 130-220
• Friday, November 18th

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List of Network Solids

• Network solids commonly contain C or Si
• Diamond, graphite, silicon, silicon carbide
• Network solids can contain metals with oxygen
  that form neutral species
• Silicates, Titania, Alumina, Arsenic Oxide
• Network solids can contain small n2 atoms with
  small electronegativity differences
• Boron Nitride

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Metallic Solids

• Metallic solids have highly delocalized valence
  orbitals. Produces a sea of mobile valence
  electrons.
• Metals in group 1 are soft, have low melting
  points, and have poor electrical conductivity.
• Metals are ductile and malleable.
• Metals in the middle of the d-block are very
  strong and have the highest melting points.
  (Tungstens MP 3407 C). Have high numbers of
  valence electrons that can occupy bonding
  orbitals in the metal lattice.
• Metals in group 11 (Copper, Silver, Gold) are
  have high electrical conductivity.

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Ionic Solids

• Ionic solids contain cations and anions strongly
  attracted to each other by electrical forces.
• Many ionic solids have metal cations and
  polyatomic anions (i.e. KNO3, CuSO4, BaCO3)
• Rare earth ionic solids can be superconductors
  (at low temperatures, resistivity can be removed)
• New materials have been reducing the
  superconductivity threshold temperature upwards.
• Dr. Chris Wiebes group has been looking at
  materials that can be used for superconductors.

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Superconductors

• Used in Nuclear Magnetic Resonance (NMR) and in
  Magnetic Resonance Imaging.
• Plans for trains on frictionless tracks.
• Possible future motors and electrical generators.

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Solid Classification Problem

• Classify each as either an ionic, network,
  molecular, or metallic solid.
• Pt, P4, Ge, As2O3, (NH4)3PO4

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Solutions

• A solution is a homogenous mixture of two or more
  substances.
• A solvent is the predominant substance.
• A solute is a minor substance in the mixture.
• Solutions can be in gas, liquid, or solid phases
  where the solvent determines the solution state.

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Solution Concentration

• Three common ways to describe solution
  concentration.

 
 
 
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Mole Fraction
 

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For Gases
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Molality Problem

• Determine the molality of a 5 by mass solution
  of C6H12O6 in water.

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Mole Fraction Problem

• An aqueous solution containing 16.0 NaCl by
  mass has a density of 1.096. What is the mole
  fraction of NaCl in this solution?

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Solubility Definitions

• Miscible substances form solutions in all
  proportions.
• An insoluble solute does not dissolve appreciably
  in a solvent.
• A saturated solution has a the maximum
  concentration of solute that can dissolve said
  to be the solubility of the compound.
• Solubility is temperature dependent.
• The solubility of a solid in a liquid increases
  with increasing temperature while the solubility
  of a gas in a liquid decreases with increasing
  temperature.

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Solubility and Intermolecular Forces

• Like dissolves like
• Mix water and methanol (both polar) the H2O-H2O
  attractive forces and CH3OH-CH3OH attractive
  forces are replaced with CH3OH-H2O attractive
  forces miscible.
• Octane and cyclohexane (both non-polar) only have
  dispersion forces, so there are not strong
  attractive forces to overcome - miscible.

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Solubility and Intermolecular Forces

• Octanol and water are not miscible due to strong
  forces between H2O-H2O bonds only replaced by
  dispersion forces.
• Acetone has intermediate polarity and can
  interact with other substances in multiple ways.

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Solubility of Solids

• Remember there are 4 types of solids bonding in
  the solid controls ability to dissolve.
• Network solids cannot dissolve since they would
  need to break strong covalent bonds.
• Metals do not dissolve as they have extensive
  delocalized bonding networks.
• Molecular solids have individual molecules bound
  by dispersion forces, dipole forces and/or
  H-bonding dissolution is possible.
• Polar molecules more soluble in more polar
  solvents.

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Solubility of Solids Molecular Solids

• Polar molecules dissolve well in water
  particularly if H-bonding is present.
• Glucose can form 5 H-bonds.
• Non-polar molecules dissolve well in fat tissues.
• Predominant interactions are dispersion forces.

Glucose surrounded by water
Cholesterol
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Solubility of Solids Ionic Solids

• Ionic solids or salts have large
  electronegativity differences between atoms so
  there are full formal charge separations.
• These interactions are strong, but strong
  ion-dipole interactions are formed in polar
  solvents when solvated.
• Water molecules will orient around the ions.

Ionic solids have large solubilities in polar
solvents and small solubilities in non-polar
solvents.
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Alloys

• Metals cannot dissolve in common solvents, but
  can dissolve in or otherwise mix with other
  metals. Only Hg can be a metal liquid to
  dissolve other metals forms amalgams.
• Some mixtures are true solutions (Brass as copper
  and Zinc)
• Others are heterogenous mixtures (Solder as lead
  and Tin)

Can also mix mixtures through substitution or
interstitial addition.