EXAM 4 - CHEM-101

General Properties of gases

Highly compressible, expand without limit, occupy containers uniformly and completely, diffuse and mix rapidly, exert pressure on their surroundings.

Kinetic-Molecular Theory

A gas consists of many particles, either atoms or molecules, moving about at random with no attractive forces between them.

Space occupied by gas particles

The amount of space occupied by the gas particles is much smaller than the amount of space between particles.

Average kinetic energy of gas particles

Average kinetic energy of gas particles is proportional to the Kelvin temperature.

Collisions of gas particles

Collisions of gas particles do not lose energy.

Gas Diffusion

Gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic energy.

Gas Effusion

Process by which a gas escapes from one compartment of a container to another by passing through a small opening.

Gas laws

Generalizations that describe the relationships among the amount (moles), pressure, temperature, and volume of a gas.

Standard atm

1 standard atm = 760 mm Hg = 29.9 inches = 34 feet of water.

Pascal, Pa

1 atm = 101.325 kPa.

Boyle's law

The volume of a fixed mass of gas is proportional to the applied pressure at constant temperature.

Charlee's law

The volume of a fixed mass of gas is directly proportional to its Kelvin temperature if the pressure is kept constant.

Gay-Lussac's Law

The pressure of a fixed mass of gas is directly proportional to its Kelvin temperature if the volume is kept constant.

Avogadro's Law

The volume of a gas is directly proportional to the number of moles of gas present if the temperature and pressure are kept constant.

Avogadro's hypothesis

Equal volumes of different gases, measured at the same temperature and pressure, contain equal numbers of molecules.

Combined gas law

Expression obtained from mathematically combining Boyle's, Charlee's, and Gay-Lussac's Laws.

Ideal Gas Law

A gas law that describes the relationships among the four variables temperature, pressure, volume and moles of a gas for a gaseous substance under one set of conditions.

Standard Temperature and Pressure (STP)

0*C and 1 atm. Standard molar volume = 22.41L per mol at STP.

Dalton's Law of Partial Pressure

The total pressure exerted by a mixture of gases is the sum of the partial pressures of the individual gases.

Partial pressure

The pressure that a gas in a mixture would exert if it were the only gas present under the same condition.

Deviations From Ideal Behavior

Volume of real gases are greater than predicted by Boyle's law because gases do have finite, incompressible volumes.

Real gases deviations

Deviations are greatest at high pressures (where the volume available to the gas is small).

Real gases deviations from Charlee's law

Volumes of real gases are less than predicted by Charlee's law because gases do have intermolecular forces of attraction.

Properties of Liquids

Definite volume and indefinite shape, high density, small compressibility, small thermal expansion.

Boiling point (bp)

The temperature at which the vapor pressure of the liquid equals the external pressure on the liquid.

Normal boiling point (nbp)

The temperature at which the liquid boils under a pressure of 760 mm Hg (1 atm).

Surface tension

The energy required to increase the surface area of a liquid by a unit amount.

Exothermic process

Processes such as sublimation, melting, and evaporation.

Endothermic process

Processes such as deposition, condensation, and freezing.

Change of states

Process in which a substance is transformed from one physical state to another physical state.

Heat of Fusion

The amount of heat energy absorbed in converting one gram of a solid to the liquid at the solid's melting point.

Heat of Vaporization

The amount of heat energy absorbed in converting one gram of a liquid to a gas at the liquids boiling point.

Heating Curve

Depicts the changes that occur by the addition of heat (at a constant rate) to a solid at a temperature below its melting point until it becomes a gas at a temperature above its boiling point.

Intermolecular Forces

An attractive force that acts between a molecule and another molecule.

Types of Intermolecular Forces

Three types: 1. Dipole-dipole 2. Dispersion (London) forces 3. Hydrogen bonding.

Dipole-Dipole

An intermolecular force between two polar molecules.

Dispersion Forces

A weak, temporary dipole-dipole interaction that occurs between an atom or molecule (polar or nonpolar) and another atom or molecule (polar or nonpolar).

Hydrogen Bonding

An attractive interaction involving a hydrogen atom covalently bonded to a small, very electronegative atom (F, O, or N) and an unshared pair of electrons on another small, very electronegative atom (F, O, or N).

Solid

The physical state characterized by dominance of potential energy over kinetic energy.

Crystalline solid

A solid that is characterized by a regular three-dimensional arrangement of the atoms, ions, or molecules present.

Crystal lattice

The highly ordered pattern of particles found in a crystalline solid.

Crystal lattice sites

The positions occupied by the particles in the lattice.

Ionic solid

A solid that consists of positive and negative ions arranged in such a way that each ion is surrounded by nearest neighbors of opposite charge.

Polar molecular solid

A solid that has polar molecules at the crystal lattice sites.

Nonpolar molecular solid

A solid that has nonpolar molecules (or atoms in the case of the noble gases) at the crystal lattice sites.

Covalent network solid

A solid that has atoms that are linked together by covalent bonds into a vast three-dimensional array at the crystal lattice sites.

Metallic solid

A solid that has metal atoms occupying the crystal lattice sites.

Properties of Ionic Solids

Hard but brittle, solids with high melting points and boiling points, poor conductors of heat and electricity except when molten, high heats of fusion and vaporization, excellent conductors when dissolved in water.

Properties of Covalent Network Solids

Very hard; brittle, extremely high melting points and boiling points, insulators, very high heats of fusion and vaporization, nonvolatile, insoluble in all common solvents.

Examples of Covalent Network Solids

Diamond and graphite, silicon carbide, silicon dioxide, boron nitride.

Properties of Molecular Solids

Soft; easily deformable, gases, liquids, or solids of low melting point, volatile, low heats of fusion and vaporization, insulators.

Properties of Metallic Solids

Very soft to hard, often malleable and ductile, very low to very high melting point, variable heats of fusion and vaporization, excellent conductors of heat and electricity in the solid and molten states, metallic luster.

Like Dissolves Like

The more similar the intermolecular forces are between solute and solvent, the greater the solubility.

Solute

Dissolves in the solvent.

Solvent

Does the dissolving.

Miscible

Substances that mix in any proportion to form a homogenous solution.

Saturated Solution

A solution that contains the maximum amount of solute that can be dissolved under conditions at which the solution exists.

Supersaturated Solution

Contains more dissolved solute than that needed for a saturated solution.

Unsaturated Solutions

Contains less solute than the maximum amount that could dissolve.

Electrolyte

A substance that produces ions and therefore conducts electricity when dissolved in water.

Strong electrolyte

A substance that ionizes completely when dissolved in water.

Weak electrolyte

A substance that is only partly ionized in water.

Nonelectrolyte

A substance that does not produce ions when dissolved in water.

Osmosis

The passage of solvent through a semipermeable membrane separating two solutions of different concentration.

Osmotic Pressure

The amount of external pressure applied to the more concentrated solution to halt the passage of solvent molecules across a semipermeable membrane.

Colligative Properties

The higher the concentration of solute particles in solution, the lower the vapor pressure and freezing point, and the higher the boiling point and osmotic pressure.

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