Ch. 8: The Gas Phase Flashcards
What is the mathematical relationship between all the units for pressure?
1 atm = 760 mmHg = 760 torr = 101.325 kPa
What is STP?
Standard temperature and pressure = 273K, 1 atm
Is the pressure on top of a mountain higher or lower than on regular ground?
Lower
What is an ideal vs real gas?
Ideal: a hypothetical gas with molecules that have no intermolecular forces and occupy no volume
Real: display intermolecular forces and occupy volume, they deviate from ideal behavior under high pressures and low temperatures
What is the ideal gas law equation?
PV=nRT
What is density?
mass per unit volume of a substance
How is density mathematically related to the ideal gas law?
PV = nRT n = m (g) / molar mass (g/mol) PV = (m/M)RT PM = (m/V) RT PM/RT = density
density = m/V
How many liters does 1 mole of a gas at STP occupy?
22.4 L
What is Avogadro’s principle?
All gases at constant temperature and pressure occupy volumes directly proportional to the number of moles of gas present. As the # of moles of gas ↑, volume ↑ proportionally.
What is Boyle’s Law?
At constant temperature, the volume of a gas is inversely proportional to its pressure.
P₁V₁ = P₂V₂
What is Charles’s Law?
At constant pressure, the volume of a gas is proportional to its absolute temperature.
V₁/T₁ = V₂/T₂
What is the combined gas law equation?
P₁V₁/T₁ = P₂V₂/T₂
What is Dalton’s law of partial pressures? Equations?
The total pressure of a gaseous mixture is equal to the sum of the total partial pressures of the individual components.
P(total) = Pa + Pb + Pc + …
Pa = Xa * P(total)
What is a mole fraction?
Xa = moles of gas a / total moles of gas
How does the partial pressure of a gas affect it’s solubility?
As the partial pressure of a gas INCREASES, the solubility of the gas INCREASES.
How does the molar concentration of gas mathematically relate to pressure? What does this relationship tell us?
[A]₁ / P₁ = [A]₂ / P₂
This shows the solubility (mol/L) increases as pressure increases.
What equation relates kinetic energy and temperature?
KE = 3/2 (KB) T
KB = boltzman constant
What is the relationship between particle speed and temperature?
The higher the temperature, the faster the molecules move. The larger the molecules, the slower they move.
What is Graham’s Law? Equation?
Under constant temperature and pressure, the rates at which two gases diffuse are inversely proportional to the square roots of their molar masses.
r₁/r₂ = sqrt (M₂/M₁)
r is the diffuse rate
M is molar mass
The larger the molar mass, the slower the diffusion rate.
What is the difference between effusion and diffusion?
Diffusion is the mixing of gases.
Effusion is the the movement of gas particles through a small hole under pressure.
What conditions cause gases to deviate from ideal conditions?
Low temperature High pressure (low volume)
How does high pressure cause a gas to deviate from ideal to real?
As pressure increases, volume decreases. This causes particles to get pushed closer together. They start to take up a larger volume than would be predicted by the ideal gas law.
How does low temperature cause a gas to deviate from ideal to real?
As temperature decreases, the average speed of gas molecules decreases and the attractive intermolecular interactions become more significant.
What do “a” and “b” represent in the van der waals equation of state?
“a” corrects for ATTRACTIVE FORCES between molecules. It is largest for large polar gases since they will display more intermolecular interactions.
“b” corrects for the VOLUME of the gas molecules. Larger molecules have a larger b.
