The Gas Phase . Flashcards
Gas is..?
least dense phase of matter
are fluids and therefore conform to the shapes of their containers
are easily compressible
described by T, P, V, and n
1 atm =
760 mmHg = 760 Torr= 101.325 Pka
What is a simple mercury barometer?
measures incident (usually atmospheric) pressure. As pressure increases, more mercury is forced into the column, increasing its height. As pressure decreases, mercury flows out of the column under its own weight, decreasing its height.
What is STP (standard temp and pressure)?
273 K (0 C) and 1 atm
Equations for gas assume..?
negligible mass and volume of gas molecules
1 mole of an ideal gas occupies how much volume at STP?
22.4 L
What is the ideal gas law?
it describes the relationship between the four variables of the gas state for an ideal gas.
PV=nRT . R = 8.314
What is Boyle’s principle?
is a special case of the ideal gas law for which the pressure and temp are held constant; it shows an inverse relationship between volume and pressure.
What is Charle’s law?
is a special case of the ideal gas law for which temperature and the number of moles are held constant; it shows a direct relationship between temp and volume
What is Gay-Lussac’s law?
is special case of the ideal gas law for which volume and number of moles are held constant; it shows a direct relationship between temp and pressure.
What is the combined gas law?
is a combination of Boyle’s, Charle’s, and Gay-Lussac’s laws; it shows an inverse relationship between pressure and volume along with direct relationships between pressure and volume with temperature.
What is Avagadro’s principle?
it is a special case of the ideal gas law for which the pressure and temperature are held constant; it shows a direct relationship between the number of moles of gas and volume
What is Dalton’s law of partial pressure?
states that individual gas components of a mixture of gases will exert individual pressure in proportion to their mole fractions. The total pressure of a mixture of gases is equal to the sum of partial pressures of the component gases.
What is Henry’s Law?
states that the amount of gas dissolved in solution is directly proportional to the partial pressure of that gas at the surface of solution.
What is the kinetic molecular theory?
attempts to explain the behavior of gas particles. It makes a number of assumptions about the gas particles:
- gas particles have negligible volume
- they do not have intermolecular attractions or repulsions
- particles undergo random collision with each other and wall of container
- collisions are elastic
- the average kinetic energy of the gas particles is directly proportional to the temp
What is Graham’s law?
describes the behavior of gas diffusion or effusion, stating gases with lower molar masses diffuse or effuse faster than gases with higher molar masses at the same temperature.
What is diffusion?
the spreading out of particles from high to low concentrations.
What is effusion?
is the movement of gas from one compartment to another through a small opening under pressure.
What are real gases?
they deviate from ideal behavior under high pressure (low volume) and low temp conditions:
-high P, low V, or low T will occupy less V than predicted by the ideal gas law because the particle have intermolecular attractions
at high P, low V, or low T, real gases occupy more volume than predicted because particle occupy physical space
What is the van der Waals equation of state?
used to correct the ideal gas law for intermolecular attractions and molecular volume.
(P+n^2a/V^2)(V-nb) = nRT
Density of gas
p = m/V = PM/RT
combined gas law
P1V1/T1 = P2V2/T2 .
avagadro’s principle
n/V = k or n1/V1 =n2/V2
boyle’s law
PV= k or P1V1=P2V2
charle’s law
V/T= K or V1/T1 = V2/T2
guy-Lussac’s law
P/T = k or P1/T1 = P2/T2
dalton’s law for total pressure from partial pressure
PT= Pa+Pb+Pc
Dalton’s for partial pressure from total pressure
PA=XAPT
Henry’s law
[A] =kH x PA or [A]1/P1=[A]2/P2 = kH
average kinetic energy of a gas
KE = 1/2 mv^2 = 3/2 kB T . average kinetic energy of a gas particle is proportional to the absolute temperature of the gas.
root-mean-squared speed
u rms = sqrt(3RT/M)
Graham’s law
r1/r2 = sqrt(M2/M1)
Van der Waals equation of state
(P+ n^2/ V^2)(V-NB) = nRT
What is vapor pressure?
it is the pressure exerted by evaporated particles above surface of a liquid. It forces some of the gas back into the liquid phase, and equilibrium is reached between evaporation and condensation. Expressed by henry’s law
What is the Boltzman constant
1.38 x 10^-23 J/K. Serve as a bridge between macroscopic and microscopic behaviors of gases. Represents kB
Maxwell-Boltzman distribution curve shows what?
The distribution of gas particle speeds at a given temperature.
