Chemistry 2e

# Key Terms

Chemistry 2eKey Terms

absolute zero
temperature at which the volume of a gas would be zero according to Charles’s law.
Amontons’s law
(also, Gay-Lussac’s law) pressure of a given number of moles of gas is directly proportional to its kelvin temperature when the volume is held constant
atmosphere (atm)
unit of pressure; 1 atm = 101,325 Pa
volume of a gas at constant temperature and pressure is proportional to the number of gas molecules
bar
(bar or b) unit of pressure; 1 bar = 100,000 Pa
barometer
device used to measure atmospheric pressure
Boyle’s law
volume of a given number of moles of gas held at constant temperature is inversely proportional to the pressure under which it is measured
Charles’s law
volume of a given number of moles of gas is directly proportional to its kelvin temperature when the pressure is held constant
compressibility factor (Z)
ratio of the experimentally measured molar volume for a gas to its molar volume as computed from the ideal gas equation
Dalton’s law of partial pressures
total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the component gases
diffusion
movement of an atom or molecule from a region of relatively high concentration to one of relatively low concentration (discussed in this chapter with regard to gaseous species, but applicable to species in any phase)
effusion
transfer of gaseous atoms or molecules from a container to a vacuum through very small openings
Graham’s law of effusion
rates of diffusion and effusion of gases are inversely proportional to the square roots of their molecular masses
hydrostatic pressure
pressure exerted by a fluid due to gravity
ideal gas
hypothetical gas whose physical properties are perfectly described by the gas laws
ideal gas constant (R)
constant derived from the ideal gas equation R = 0.08206 L atm mol–1 K–1 or 8.314 L kPa mol–1 K–1
ideal gas law
relation between the pressure, volume, amount, and temperature of a gas under conditions derived by combination of the simple gas laws
kinetic molecular theory
theory based on simple principles and assumptions that effectively explains ideal gas behavior
manometer
device used to measure the pressure of a gas trapped in a container
mean free path
average distance a molecule travels between collisions
mole fraction (X)
concentration unit defined as the ratio of the molar amount of a mixture component to the total number of moles of all mixture components
partial pressure
pressure exerted by an individual gas in a mixture
pascal (Pa)
SI unit of pressure; 1 Pa = 1 N/m2
pounds per square inch (psi)
unit of pressure common in the US
pressure
force exerted per unit area
rate of diffusion
amount of gas diffusing through a given area over a given time
root mean square speed (urms)
measure of average speed for a group of particles calculated as the square root of the average squared speed
standard conditions of temperature and pressure (STP)
273.15 K (0 °C) and 1 atm (101.325 kPa)
standard molar volume
volume of 1 mole of gas at STP, approximately 22.4 L for gases behaving ideally
torr
unit of pressure; $1 torr=1760atm1 torr=1760atm$
van der Waals equation
modified version of the ideal gas equation containing additional terms to account for non-ideal gas behavior
vapor pressure of water
pressure exerted by water vapor in equilibrium with liquid water in a closed container at a specific temperature
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