General Chemistry - The Gas Phase

MCAT Chapter 8

Ideal gas

hypothetical gas with molecuels that have no intramolecular forces and occupy no volume

Standard temperature and Pressure (STP)

273K and 1atm

Density

ratio of mass per unit of volume of a substance

Gay Lussacs Law

relates pressure to temp

Avagadros princple

All gases at constant temp and pressure occupy volumese that are directly proportional to the number of moles of gas present

Boyles Law

A gaseous sample at constant temp, the volume of a gas is inversly proportional to pressure

Partial Pressure

The pressure exerted by each individual gas

Daltons Law of Partial Pressure

The total pressure of a gaseous mixture is equal to sum of partial pressure of individual components

Charles Law

At constant pressure, volume of gas is proportional to its absollute temp

Vapor pressure

pressure exerted by evaporated particles above the surface of a liquid

Components of Kinetic Molecular Theory

1. Gases are made up of particles with volumes that are neglible compared to the container volume

2. Gas atoms or molecules exhibit no intermolecular attractions or repulsions

3. Gas particles are in continuous, random motion, undergoing collisions with other particles and their container walls

4. Collisions between any two gas particles are elastic, meaning that there is conservation of both momentum and kinetic energy

5. The average kinetic energy of gas particles is proportional to the absolute temp of the gas and it is the same for all gases at a given temp, irreversible of chemical identity or atomic mass

Maxwell Boltzmann distribution curve

shows distribution of gas particle speeds at a given temperature

Diffusion

movement of molecules from high concentration to low concentration through a medium

Effusion

The flow of gas particles under pressure from one compartment to another through a small opening

Graham’s Law

Rate two gases diffuse are inversely proportional to the square roots of their molar masses

Vander Waals equation of state

used to correct the ideal gas law for intramolecular attractions and molecular volume