CHEM 102 Lecture Notes - Lecture 1: London Dispersion Force, Intermolecular Force, Polarizability

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8 Apr 2015

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Chem 102: general descriptive chemistry ii - lecture 1: intermolecular forces (1/13/15) Im forces: attractions between molecules: control physical properties, phase changes, vapor pressure, viscosity, boiling/melting points, strength of im forces related to the distance between particles. Intermolecular forces increase from gases to liquids to solids. Molecular shape longer, skinnier molecules have stronger forces because of increased surface area. More polar molecule higher boiling point. Dipole-dipole interaction strength increases with polarity: hydrogen bonding, strong im force, a hydrogen bond can occur when hydrogen is bonded with oxygen, nitrogen, or fluorine.

Related Questions

* Circle the intermolecular force(s) that is/are present in each of the following species. [Hint: there may be more than one correct answer.]

Ar (hydrogen bonding, dipole-dipole forces, dispersion forces)

CH4 (hydrogen bonding, dipole-dipole forces, dispersion forces)

HBr (hydrogen bonding, dipole-dipole forces, dispersion forces)

HF (hydrogen bonding, dipole-dipole forces, dispersion forces)

CHCl3 (hydrogen bonding, dipole-dipole forces, dispersion forces)

* For the following pairs of atoms/molecules, circle the species that has the higher boiling point.

Ne or Xe

Cl2 or F2

HBr or HF

HCl or HI

H2O or H2S

* Phase changes always associate with change of enthalpy. For the following situations, name the phase

transition and indicate whether the process is exothermic or endothermic.

(a) Dry ice (solid carbon dioxide) turns to gaseous carbon dioxide.

Answer:

(b) Water vapor turns to liquid water.

Answer:

(d) Iodine vapor turns to solid iodine.

Answer:

(e) Liquid helium turns to helium gas.

Answer:

* True or false

1. Intermolecular forces are stronger than ionic and covalent bonds. Answer:

2. For molecules with similar size and molar mass, those with higher polarity would have higher boiling

point. Answer:

3. Ion-dipole forces exist between ionic potassium bromide and polar water.

Answer:

4. Dispersion forces exist between argon and helium. Answer:

5. Instantaneous dipoles exist in all molecules and atoms. Answer:

6. The strength of dispersion forces depends on the molar mass but the shape of the molecules have no effect on dispersion forces. Answer:

7. Ice has a higher density than water because ice has an ordered cagelike structure. Answer:

8. Liquids with weaker intermolecular interactions have lower viscosity. Answer:

9. Viscosity decreases with increasing temperature. Answer:

10. For any molecules, the heat of vaporization is always lower than the heat of fusion because it takes more energy to make molecules to move past one another in a solid lattice. Answer:

Phase changes always associate with change of enthalpy. For the following situations, name the phase transition and indicate whether the process is exothermic or endothermic.

. Dry ice (solid carbon dioxide) turns to gaseous carbon dioxide. Answer:

. Water vapor turns to liquid water. Answer:

. Solid iron turns to liquid iron. Answer:

. Iodine vapor turns to solid iodine. Answer:

. Liquid helium turns to helium gas. Answer:

True or false

. Intermolecular forces are stronger than ionic and covalent bonds. Answer:

. For molecules with similar size and molar mass, those with higher polarity would have higher boiling point. Answer:

. Ion-dipole forces exist between ionic potassium bromide and polar water. Answer:

. Dispersion forces exist between argon and helium. Answer:

. Instantaneous dipoles exist in all molecules and atoms. Answer:

. The strength of dispersion forces depends on the molar mass but the shape of the molecules have no effect on dispersion forces. Answer:

. Ice has a higher density than water because ice has an ordered cagelike structure. Answer:

. Liquids with weaker intermolecular interactions have lower viscosity. Answer:

. Viscosity decreases with increasing temperature. Answer:

. For any molecules, the heat of vaporization is always lower than the heat of fusion because it takes more energy to make molecules to move past one another in a solid lattice. Answer:

WORD BANK:

Atomic solids

Body-centered cubic

Boiling point

Condensation

Covalent atomic solids

Crystal lattice

Crystalline solids

Distillate

Distillation

Dynamic equilibrium

Evaporation

Face-centered cubic

Freezing

Freezing point

Ionic solids

Intramolecular

Interionic forces

Intermolecular forces

Liquid State

Macromolecule

Melting

Melting point

Metallic atomic solids

Molar heat of fusion

Molar heat of vaporization

Molecular solids

Non-bonding atomic solids

Non-crystalline (amorphous) solids

Properties of Liquids

Properties of Solids

Simple cubic

Solid State

Sublimation

Surface tension

Surfactants

Vapor pressure

Vaporization

Viscosity

Wetting action

Use the Vocabulary words above to complete the following sentences words can be used more than once, some words are not be used.

d. The molecules of a ________ are in constant motion. e. The __________ of a liquid is related to the shape of the molecules that make up the liquid. f. The force of attraction that causes the surface of a liquid to contract and form a âbeadâ or spherical drop is called? _________ _______ g. Chemical that reduce surface tension are called? __________ h. A liquids ability to spread out evenly over a surface as a thin film is called itâs? _________ _______ i. ____________ is the process by which molecules of a liquid break away and go into the gas phase. j. When the molecules of a volatile liquid jump to gas phase it is called _________. k. The reverse of evaporation (the conversion of a vapor to a liquid) is called? _________ l. When the rate at which the water is evaporating is equal to the rate at which the water vapor is condensing, you have established a __________ _________. m. ________ _______ is the partial pressure of a gas in dynamic equilibrium with its liquid. n. ________ _______ is when the vapor pressure equals the atmospheric pressure. o. Boiling point can be used to purify a solution of two or more substances by ________. p. The condensed vapor sample is called the? ________ q. The exact quantity of heat required to vaporize 1 mole of a liquid at constant pressure and temperature is called the ________ ________ ___ __________. r. In ________________ __________ the particles do not have a definite or regular order (there is no repeating pattern throughout the solid). s. In ____________ __________, the particles are arranged in regular, systematic patterns called a ________ _________. t. The three different types of crystal lattices based on the cube are? ________ ______, _____________ ______, and ___________, ________. u. The three types of atomic solids include _________ _____, ___________ ______, and __________ ________.

CHEM 102 Lecture Notes - Lecture 1: London Dispersion Force, Intermolecular Force, Polarizability

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