Gas Laws/State Of Matter CH 6 & 7 Flashcards
What are the laws that make up the Empirical gas laws
Boyle’s law, Charle’s Law, and Avogadro’s Law
What does Boyle’s Law state
When temperature is constant, Volume is inversely proportional to pressure
As pressure goes up, volume goes down
As pressure goes down, volume goes up
P1V1=P2V2
What does Charle’s Law state
When pressure and amount of gas are constant, volume is directly proportional to temperature
As temp goes up, volume goes up
As temp goes down, volume goes down
V1/T1 = V2/T2
*note: Not really true. Gas in a contained cylinder will have an increase in pressure as the temp goes up and VOLUME remains constant.
*Gay Lussc’s Law is a variation of Charles law which addresses this discrepancy (P1/T1=P2/T2)
What does Avogadro’s Law state
When temperature is constant, the volume of gas is directly proportional to the number of moles of gas
Volume goes up, #moles goes up
Volume goes down, #moles goes down
V1/n1=V2/n2
What does Gay-Lussac’s Law state
It is a variation of Charle’s law and states that when volume is constant, the pressure of a gas is directly proportional to the absolute temperature
Temp goes up, pressure goes up
Temp goes down, pressure goes down
P1/T1 = P2/T2
What is the combined gas laws?
It combines Boyles, Charles, and Avogadro’s Law
P1V1/n1T1 = P2V2/n2T2
What is the Ideal Gas Law
It describes the behavior of an ideal gas under all conditions, but it does not account for real gases that we deal with in real life.
PV=nRT
R is constant
n = # moles
P = pressure
V = volume
T = temp in kelvin
What is the universal gas constant?
R is the universal gas constant
R = PV/nT
R = 0.08206 Latm/molK
What does R equal
R = 0.08206 Latm/molK
What is STP
The Standard Temperature and Pressure
It is a commonly cited set of conditions that helps determine R when conditions are specified
STP is defined to be exactly zero degrees C or 273.15K with a standard pressure 1 Bar
1Bar = 100kPa = 1atm = 760 torr = 101325 Pa or 101.325 kPa
What is the standard molar volume of a gas
The volume that exactly 1 mole of ideal gas occupies under STP conditions
1 mol = 22.71 L
What do we need to know in order to calculate gas density
mass and volume
Density = m/V
How do we calculate density if we have known temperature and pressure
use the ideal gas law (n=PV/RT) to get moles of each component
then obtain the molecular mass of each component
Multiply n by the molecular mass of each component to get the fraction of mass
Substitute those fractions into the Density = m/v
Volume should be given and remember gas is non-reactive and their volumes are additive (so if N2=0.79L and O2=0.21L the the V=0.79+0.21=1.0L)
What does Dalton’s law state
the total pressure of a gas mixture is equal to the sum of partial pressures of each component of gas
Ptotal = P1 + P2…..+Pn
To calculate partial pressure,
Pi = Xi * Ptotal
where Xi is the mole fraction in a mixture
And Ptotal = nRT/V
What is relative humidity
the measure of the saturation of water in the air
One way to calculate relative humidity is to divide the amount of water in the air by the solubility of water in the air
Relative humidity is a function of temperature
as temp goes up solubility of water in air goes up
What is the solubility of water in the air
It is the maximum amount of water that a given volume of air can accommodate
How much N2 and O2 are in the air?
79%N2 and 21% O2
We usually measure water vapor pressure in air as
47mmHg
What is the dew point temperature
it is the condensation formed when a sample is cooled to a temperature where the actual concentration of water exceeds the solubility of water in air
How can we calculate of relative humidity using vapor pressure and partial pressures
RH = partial pressure of water/vapor pressure of water all times 100%
what is the Kinetic Molecular Theory of Gases
It describes ideal gases based on 4 tenents
what are the 4 tenants of the kinetic molecular theory of gases
1) Gases consist of small particles while volume is negligible compare to the volume of gas
- not really true: real gas at high pressures crows more gas molecules into same volume
2) Gas molecules are in constant, random motion
3) The molecules in the sample show a range of kinetic energies, but the average KE depends only on the temperature
4) There are no attractive or repulsive forces between the gas particles, so all Collins are elastic
- not really true: real gases do have an attractive force as seen in liquid state & low temperatures
The average KE is dependent on what
Temperature
KE = 3/2kT
k= Boltzmann’s constant
Boltzmann’s constant (k) equals
1.38 x10^-23 J/K