Ch 5 Gases Lecture Notes

A collection of important terms and definitions related to gases, including laws, measurements, and behavior.

Pressure

The force exerted per unit of surface area.

Pascal (Pa)

The SI unit of pressure, equivalent to one Newton per square meter.

Standard Atmosphere (atm)

The pressure exerted by a mercury column of exactly 760 mm in height.

Barometer

A device developed to measure atmospheric pressure using liquid mercury.

Liquid Pressure

Pressure of a liquid depends on the height of the liquid column and the density of the liquid.

Boyle's Law

For a fixed amount of gas at constant temperature, the volume occupied by a gas is inversely proportional to the applied external pressure.

Charles's Law

At constant pressure, the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature.

Avogadro's Law

At a fixed temperature and pressure, the volume occupied by a gas is directly proportional to the amount of gas.

Ideal Gas Law

A combination of Boyle’s law, Charles’s law, and Avogadro's law expressed as PV=nRT.

Molar Volume

The volume occupied by one mole of an ideal gas at standard temperature and pressure.

Density of a Gas

The mass of the gas divided by its volume.

Dalton's Law of Partial Pressures

In a mixture of unreacting gases, the total pressure is the sum of the partial pressures of the individual gases.

Mole Fraction

The fraction of all molecules in a mixture that is contributed by a specific gas.

Mean Free Path

The average distance a molecule travels between collisions.

Diffusion

The migration of molecules as a result of random molecular motion.

Effusion

The escape of gas molecules from their container through a tiny orifice into another container.

Graham’s Law of Effusion

The rate of effusion of gas A compared to gas B is inversely proportional to the square root of their molar masses.

Real Gas Behavior

Actual behavior of gases that deviates from ideal gas behavior due to molecular volume and intermolecular forces.

Van der Waals Equation

An equation that corrects the ideal gas law for intermolecular forces and molecular volume.

Kinetic Molecular Theory (KMT)

A model that explains the behavior of gases in terms of particles in motion.

Standard Conditions

Standard temperature and pressure conditions for gas studies, typically 0°C and 1 atm.

Conversion of Pressure Units

The process of converting between different units of pressure such as atm, mmHg, and kPa.

Gas Laws Summary

Boyle’s Law, Charles’s Law, and Avogadro’s Law are fundamental relationships among gas properties.

Elastic Collisions

Collisions between gas molecules that conserve kinetic energy before and after the collision.

Atmospheric Pressure

The pressure exerted by the weight of the atmosphere at a given point.

Inversely Proportional

A relationship where an increase in one quantity results in a decrease in another.

Directly Proportional

A relationship where an increase in one quantity results in an increase in another.

Absolute Zero

The theoretical temperature at which a system's entropy reaches its minimum value.

Molar Mass (M)

The mass of one mole of a substance, usually expressed in grams per mole.

Vapor Pressure

The pressure exerted by a vapor in equilibrium with its liquid or solid form.

Collecting Gas Over Water

A method for gathering gas that accounts for the water vapor pressure.

Gas Stoichiometry

The calculations involving the amounts of reactants and products in gas reactions.

Stoichiometric Factors

Ratios derived from the coefficients of a balanced chemical reaction.

KMT and Pressure

Explains how pressure is caused by molecules colliding with the walls of their container.