assumptions of the ideal gas model:
- particles in a gas are in constant, random, straight-line motion
- forces of attraction (intermolecular forces between particles is negligible
- collisions between particles or with the walls of the container are elastic
- distance between particles is much greater than the size of the particles ⇒ gas particles have negligible volume
- kinetic energy of the particles in a gas is directly proportional to the absolute T(K)
physical characteristics of gasses
- V = volume [L, dm3]
- P = pressure [Pa = N/m^2]
- the force the gas exerts on a given area of the container in which it is contained
- T = temperature [K]
- n = amount of substance [mol]
Avogadro’s law
⇒ at a constant P and T, the V of a gas is directly proportional to the number of moles
V1/n1 = V2/n2
molar volume
Vm = V/n = RT/P = M/density = [dm^3/mol]
STP => Vm = 22.7 dm3/mol
Boyle’s law
⇒ at a constant T, P and V are inversely proportional
P1V1 = P2V2
Charles’ law
⇒ at a constant P, V is directly proportional to T
V1/T1 = V2/T2
Gay-Lussac’s law
⇒ at a constant V, P and T are directly proportional
P1/T1 = P2/T2
proportionality of the physical characteristics of gasses
n = const
P1V1/T1 = P2V2/T2
ideal gas equation
PV = nRT
gas constant
R = 8.314 J/molK = 8.314 dm^3kPa/molK
ideal vs real gas conditions
ideal gas conditions ⇒ high T, low P
real gas conditions ⇒ low T, high P
T in real gas conditions and its effects
- low T
- kinetic energy of particles is reduced
- in collisions, intermolecular forces form ⇒ molecules may not rebound elastically
P in real gas conditions and its effects
- high P
- more molecules in a reduced space
- V of the molecules becomes a significant part of the V of the gas
Van der Waals equation
real gas equation
(P + a(n/V)^2)(V - nb) = nRT
