Ideal Gases
Imaginary Gases that perfectly fit all of the assumptions of the kinetic molecular theory
List the five assumptions of the kinetic molecular theory
1) consist of tiny particles that are far apart relative to their size.
2) Collisions between gas particles are elastic (no kinetic energy is lost in kinetic collisions)
3) gas particles are in constant, rapid motion, therefore they possess kinetic energy
The nature of gases (5 characteristics)
1) gases expand to fill their containers
2) they are fluid, they flow
3) have low density (1/1000 density of the equivalent solid or liquid)
4) gases are compressible
5) they effuse and diffuse
Elastic Collision
No kinetic energy is lost in particle collisions
Real Gas
Does not behave according to ideal gas law assumptions.
Conditions that make gases act like real gases
More polar gases
high pressures
low temperatures
Pressure
How much force applied to a given area,
caused by the collisions of molecules against the walls of a container
SI unit of pressure
newton/meter^2 = 1 pascal
1 atmosphere
101,325 Pascals (Pa)
AKA 101.325 kilopascals
Conversion factor from atm to torr
1 atm = 760 torr = 760 mmHg = 101.325 KPa
First device used for measuring atmospheric pressure
Barometer
baro means weight
meter means measure
Created the barometer, and in what century
Evangelista Torricelli, 17th century
STP
Pressure = 1 atmosphere, 760 torr, 101.325 Kpa
Temperature = 273.15 Kelvins
Molar volume of an ideal gas is 22.42 liters at STP
Boyle's Law
Pressure is inversely proportional to volume
when temperature is held constant.
P1V1=P2V2
Charles's Law
The volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin.
(P = constant)
V1/T1 = V2/T2
Gay Lussac's Law
The pressure and temperature of a gas are
directly related, provided that the volume
remains constant.
P1/T1=P2/T2
Combined Gas Law
PV/T = PV/T
Avogadro's Law
For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas (at low pressures).
V = an
AKA V1/n1 = V2/n2
a = proportionality constant
V = volume of the gas
n = number of moles of gas
Ideal Gas Law
PV = nRT
P = pressure in atm
V = volume in liters
n = moles
R = proportionality constant
= 0.08206 L atm/ mol�K
T = temperature in Kelvins
(truest when pressure < 1 atm)
Standard Molar Volume states that
Equal volumes of all gases at the same temperature and pressure contain the same number of molecules.
Equation for molar mass of a gas
M = dRT/P
(d = density)
Gas Density Units
molar mass / volume
Density at STP
22.4 g/ Liter
Formula for density
D = MP/RT
M = Molar Mass
P = Pressure
R = Gas Constant
T = Temperature in Kelvins
Who created the law of partial pressures
Dalton
Law of Partial Pressures
For a mixture of gases in a container,
PTotal = P1 + P2 + P3 + . . .
(When V and T are constant)
How to use law of partial pressures
Two gases in a container. Use ideal gas laws to find pressure of each individually. add those together to get total pressure.
Kinetic Molecular theory
Particles of matter are ALWAYS in motion
Volume of individual particles is zero.
Collisions of particles with container walls cause pressure exerted by gas. (Perfectly elastic collisions)
Particles exert no forces on each other.
Average kinetic energy �
Formula for kinetic energy of gas
KE 1/2 mv^2
formula for average kinetic temperature
KE = 3/2 RT
Diffusion
the mixing of gases.
gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties.
Rate of diffusion
rate of different gases mixing
Effusion
Passage of gas into an evacuated chamber
the process by which gas under pressure escapes from one compartment of a container to another by passing through a small opening.
Grahams law for rates of effusion and diffusion
rate = (M)^(-1/2)
Absolute Zero
0 Kelvin, no movement of particles
Proportionality constants for Ideal gas law Kilopascals
8.312 L kPa/ mol K
Proportionality constants for Ideal gas law
atm
0.08206 L atm/ mol kPa
Proportionality constants for Ideal gas law
Joules (use this in KE formulas)
8.3145 J/mol K
Mole Fraction
ratio of the number of moles of a given component in a mixture to the total number of moles in the mixture