Ch. 8: The Gas Phase Flashcards
variables that define the gaseous state
- pressure (P)
- volume (V)
- temperature (T)
- number of moles (n)
what is an ideal gas
a hypothetical gas with molecules that have no intermolecular forces and occupy no volume
ideal gas law
PV = nRT
where R = 8.21 E-2 in [L * atm] / [mol * K]
density derived from ideal gas law
p = m / V = PM / RT
were n = m (mass) / M (molar mass)
combined gas law
relationship of P, V, and T for a gas as conditions change
[P1V1] / T1 = [P2V2] / T2
how many L does 1 mole of gas occupy at STP
1 mole of ideal gas = 22.4 L at STP
Avogadro’s principle
relationship of moles and volume
n/V = k OR n1/V1 = n2/V2
number of moles of any gas is directly proportional to volume
Boyle’s law
relationship of pressure and volume
PV = k or P1V1 = P2V2
pressure and volume are inversely proportional
Charle’s law
relationship of volume and temperature
V/T = k or V1/T1 = V2/T2
volume and temperature are directly related
Gay - Lussac’s law
relationship of pressure and temperature
P/T = k or P1/T1 = P2/V2
pressure and temperature are directly related
partial pressure
pressure exerted by each individual gas in a container when those gases do not combine with each other
equation for total pressure from partial pressure
Pt = Pa + Pb + Pc …
total pressure is equal to the sum of all the partial pressures
equation for partial pressure of a gas
Pa = Xa * Pt
where Xa = moles of gas a / total moles of gas
vapor pressure
pressure exerted by evaporated particles above the surface of the liquid
equation for vapor pressure of a gas
[a] = kH * Pa
OR
[a]1/P1 = [a]2/P2 = kH
where [a] is concentration of a in sol’n, kH is Henry’s constant and Pa is the partial pressure of the gas
equation for kinetic energy of a gas particle
KE = 1/2 m * v^2 = 3/2 kB * T
where kB is Boltzmann constant = 1.38 E -23 J/K
**kinetic energy of a gas particles is directly proportional to speed of particles (higher temp = faster, larger = slower) **
equation for average gas particle speed
u rms = sqrt [3RT / M]
how do gas particles diffuse
same as liquids, from areas of high to low concentration
Graham’s Law
relationship between diffusion rates and molar masses
r1 / r2 = sqrt M2/M1
when molar mass is four times greater it moves (diffuses) half as fast
effusion
flow of gas particles under pressure from one compartment to another through a small opening
RATE same as diffusion (twice as fast for one quarter mass)
what does the van der Waals equation correct for
the attractive forces between molecules and the volume of molecules
