Honors Chemistry: Gas Laws and Intermolecular Forces

Postulates of the Kinetic Molecular Theory

1. Particles are so small compared with the distances between them that the volume of the individual particles can be assumed to be negligible (zero)

2. The particles are in constant motion and move in straight paths. The collisions of the particles with the walls of the container are the cause of the pressure exerted by the gas

3. The particles are assumed to exert no forces on each other; they are assumed neither to attract nor to repel each other

4. The average kinetic energy of a collection of gas particles is assumed to be directly proportional to the Kelvin temperature of the gas

Absolute Zero

the temperature at which all particles stop motion (0 Kelvin)

Atmospheric Pressure

the pressure exerted by a column of air from the top of the atmosphere to the surface of the earth

Barometer

measures the pressure exerted by the gases in the atmosphere

Maxwell-Boltzmann Distribution

a graphical representation to show how the speeds of molecules are distributed for ideal gases

Root Mean Square Velocity

(3RT/M)^1/2

Effusion

describes the passage of a gas through a tiny orifice into an evacuated chamber

Diffusion

the mixing of gases

Graham’s Law of Effusion

Rate of Effusion for G₁/Rate of Effusion for G₂ = (M₂)^1/2/(M₁)^1/2

Boyle’s Law

P₁V₁=P₂V₂

Charles’ Law

V₁/T₁ = V₂/T₂

Gay-Lussac’s Law

P₁/T₁=P₂/T₂

Combined Gas Law

P₁V₁/T₁=P₂V₂/T₂

Avogadro’s Law

V₁/n₁=V₂/n₂

Standard Temperature and Pressure (STP)

1 mol = 273 K = 1 atm = 22.4 L

Ideal Gas Law

PV=nRT

Ideal Gas Constant (R)

0.08206 L x atm/ mol x K

Partial Pressure

the pressure of each gas in a mixture

Dalton’s Law

P_T=P₁+P₂+P₃…

Dipole-Dipole Forces

occurs when a polar bond has an unequal sharing of electrons and causes a partial positive and a partial negative to occur.

Hydrogen Bonding

Only occurs when hydrogen is bound to oxygen, nitrogen, and fluorine

London Dispersion Forces

instantaneous dipole that occurs accidentally in each atom induces a similar dipole in a neighboring atom (the larger the molecule the stronger the LDF)

As intermolecular forces increase, what happens to each of the following?

Boiling Point: inc.

Viscosity: inc.

Surface Tension: inc.

Freezing Point: inc.

Vapor Pressure: dec.

Heat of Vaporization: inc.