Chemistry Gases Flashcards
The ___ is generally defined by four variables: pressure (P), volume (V), temperature (T) and number of moles (n).
state of a gaseous sample
1 ___ = 10^5 Pa = 760 mm Hg = 760 torr
atmospheres (atm)
Gases are also often discussed in terms of ___ (STP), which refers to conditions of 273.15 K (0 degrees Celsius) and 1 atm
standard temperature and pressure
An ideal gas represents a hypothetical gas whose ___ have no intermolecular forces and occupy no volume
molecules
Subsequently, for a given ___ under two sets of conditions, the following equation can be derived:
P sub 1 V sub 1 = k sub 1 = P sub 2 V sub 2 or simply P sub 1 V sub 1 = P sub 2 V sub 2
where k is a proportionality constant and the subscripts 1 and 2 represent two different sets of conditions (volume and pressure are inversely proportional)
sample of gas
The volume of a gas is directly proportional to its absolute ___
V/T = k or V sub 1 / T sub 1 = V sub 2 / T sub 2
where k is a constant and the subscripts 1 and 2 represent two different sets of conditions
temperature
At a ___ and pressure, the volume of the gas will be directly proportional to the number of moles of gas present; therefore, all gases have the same number of moles in the same volume
constant temperature
Avogadro’s ___:
n/V = k or n sub 1 / V sub 1 = n sub 2 / V sub 2
principle
A theoretical gas that has volume-pressure-temperature behavior that can be completely understood by the ideal gas equation is known as an “ideal gas”.
PV = nRT
The constant R is known as the gas constant. Under STP, one mole of ideal gas has a volume of 22.4 L. R = 0.0821 L atm/mol K.
The ___ may also be expressed in many other units; another common value is 8.314 J/ (K mol), which is derived when the SI units of pascals (for pressure) and cubic meters (for volume) are substituted into the ideal gas law
gas constant
In addition to standard calculations to determine the ___, volume, or temperature of a gas, the ideal gas law may also be used to determine the density and the molar mass of a gas
pressure
PV = nRT where n = m (mass in g)/MM (\_\_\_) therefore PV = (m/MM)(RT) and P(MM)/RT = m/v = d
molar mass
Another way to find the density of a gas is to start with the volume of a mole of gas at STP, 22.4 L, calculate the effect of pressure and temperature on the volume, and finally calculate the ___ by dividing the mass by the new volume
density
The closer the temperature of a gas is to its boiling point, the less ___ is its behavior
ideal
Van der Waals Equation.
[P + a(n/V)^2][(V/n)-b] = RT
In this equation P is the measured ___, a is the correction factor to account for intermolecular forces, n is the number of moles of gas present, V is the measured volume, and b is a correction factor to account for the finite size of the molecules
pressure
The ___ exerted by each individual gas is called the partial pressure of that gas
pressure
The total ___ of a gaseous mixture is equal to the sum of the partial pressures of the individual components
P sub T = P sub A + P sub B + P sub C and so on.
P sub A = P sub T X sub A
X sub A = [n sub A (moles of A)/n sub T (total moles)]
pressure
Assumptions of the Kinetic Molecular Theory
Gases are made up of ___ whose volumes are negligible compared to the container volume
Gas atoms or molecules are inert and exhibit no intermolecular attractions or repulsions
Gas particles are in continuous, random motion, undergoing collisions with other particles and container walls
Collisions between any two gas particles are elastic, meaning that there is no overall gain or loss of energy
The average kinetic energy of gas particles is proportional to the absolute temperature of the gas and is the same for all gases at a given temperature
particles
According to the ___, the average kinetic energy (and therefore average velocity) of a gas particle is proportional to the absolute temperature of the gas:
KE = (1/2)mv^2 = (3/2)kT
where k is the Boltzmann constant
kinetic molecular theory of gases
At a given temperature, all ___ will have the same kinetic energy, but this does not mean those gases are behaving identically. The heavier the gas, the slower it will move.
gases
A ___ shows the distribution of speeds of gas particles at a given temperature
Maxwell-Boltzmann distribution curve
The kinetic molecular theory of gases predicts that heavier ___ diffuse more slowly than lighter ones because of their differing average molecular speeds
gas molecules
(r sub 1/ r sub 2)=(MM sub 2/MM sub 1)^(1/2) = square root (MM sub 2/ MM sub 1)
where r sub 1 and MM sub 1 represent the ___ rate and molar mass of gas 1, respectively , and r sub 2 and MM sub 2 represent the diffusion rate and molar mass of gas 2
diffusion
___ is the flow of gas particles under pressure from one compartment to another through a small opening
effusion
