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Flashcards in The Gas Phase Deck (20):

STP condictions

T= 273 K (0 degree C)
P= 1atm
-used with gases


Standard conditions

T= 298K (25 degree C)
P= 1atm
Concentration= 1M


Characteristics of gases

Gases are compressible fluids with rapid motion, large intermolecular distances, and weak intermolecular forces


Mercury Barometer

-When the external air exerts a higher force than the weight of the mercury in the column, the column rises.
-When the external air exerts a lower force than the weight of the mercury, the column falls


Ideal Gases

Represents a hypothetical gas with molecules that have no intermolecular forces and occupy no volume


Ideal Gas Law

R= .0821



Ratio of the mass per unit volume of a substance
Shortcut to finding density- ρ = m/V = PM/RT


Avogadro's Principle

-Which states that all gases at a constant temperature and pressure occupy volumes that are directly proportional to the number of moles of gas present
-n1/V1 = n2/V2
-As the number of moles of gas increases, the volume increases in direct proportion


Boyle's Law

P1V1 = P2V2
As pressure increases, volume decreases (inverse log)


Charles Law

V1/T1 = V2/T2
As temperature increases, volume increases (linearly)


Gay-Lussac's Law

P1/T1 = P2/T2
As temperature increases, pressure increases (linearly)


Dalton's Law of Partial Pressure

Pa = XaPt
Pa is the partial pressure of the gas a
Xa is the mole fraction of a, which is the moles of gas a/ total moles of gas


Henry's Law

[A] = kH x Pa or [A1]/P1 = [A2]/P2 = kH
-[A] is the concentration of A in solution, kH is Henry's constant, and Pa is the partial pressure of the gas
-Solubility of a gas will increase with increasing partial pressure of the gas


Kinetic Molecular Theory Assumptions

-Gas made of particles whose volumes are negligible compared to container volume
-Gas molecules exhibit no intermolecular forces
-Gas is in continuous, random motion, undergoing collisions with other particles and the wall
-Collisions are elastic, meaning that there is conservation of both momentum and kinetic energy
-Average kinetic energy of gas particles is proportional to the absolute temperature of the gas, and it is the same for all gases at a given temperature, irrespective of chemical identity or atomic mass


Kinetic Molecular Theory of Gases

-Average kinetic energy of a gas particle is proportional to the absolute temperature of the gas
KE = 3/2kbT where kb is the Boltzann's constant (1.38x10^23 J/K)


Root Mean Square Speed (urms)

urms = sqrt(3RT/M)


Maxwell-Boltzmann Distribution Curves

The more massive the gas particles, the slower their average speed


Graham's Law

r1/r2 = sqrt(M2/M1)


Deviation Due to Pressure

-AS the condensation pressure for a given temperature is approached, intermolecular attraction forces become more and more significant
-As the temperature of a gas is decreased, the average speed of the gas molecules decreases and the attractive intermolecular forces become increasingly significant


Van der Waals Equation of State

(P + n^2a/V^2)(V-nb) = RT
-a corrects for the attractive forces between molecules. The more polarizable the molecule, the larger the a value
b corrects for the volume of the molecules themselves. Larger molecules thus have larger values of b.