CH. 1.2 - THE IDEAL GAS LAW Flashcards
Explain Dalton’s Law of Partial Pressures: Pₜ = P₁ + P₂ + P₃
The total pressure exerted by a mixture of gases is the sum of all the partial pressures of these gases.
The sum of all mole fractions should equal…
1
In a container filled with different gases, how will the gases behave?
Each gas will maintain its own behaviors and behave as its alone in this container
What is the concept behind the molar volume of gas?
At a standard temperature and pressure, any gas will take up the same amount of space (have the same volume)
At STP, what is the volume of space 1 mole of gas will take up
22.4L
What are the two ways/equations we can use to find the mole fractions of a mixture?
- Xᵢ = nᵢ/nₜ
- Xᵢ = Pᵢ/Pₜ
we can use moles or pressure to find the mole fractions
Why can we use moles or pressure to find the mole fractions of a gas mixture?
because moles and pressure are directly related at a constant temperature and volume
At equilibrium, the rates of evaporation and condensation will be the same, meaning the pressure of H20 (g) will… _________
remain constant
When is equilibrium reached with water vapor?
when the rate of evaporation = the rate of condensation
What happens when equilibrium is reached with water vapor?
the amount of water vapor in the air stays constant and so does the vapor pressure
What equation do you use to find the total pressure of the gas in the flask when dealing with water vapor?
Pₜ = Pₐᵢᵣ + Pᵥᵥₐₜₑᵣ ᵥₐₚₒᵣ
where Pₐᵢᵣ = pressure exerted by the air,
and Pᵥᵥₐₜₑᵣ ᵥₐₚₒᵣ = pressure from the water vapor
What does the vapor pressure of any liquid depend on?
temperature
When temperature INCREASES, what happens to the vapor pressure?
the molecules in the liquid have more energy and be more likely to evaporate, which will INCREASE the vapor pressure
Why do volatile liquids have higher vapor pressures at a given temperature?
They have lower boiling points and evaporate easily, meaning that they need less energy to change states.
How do you find the average molar mass of a mixture?
MM = (Xₐ* MMₐ) + (Xb* MMb) + (X꜀* MM꜀)
where X is the mole fraction of the specific gas and MM is the molar mass of that specific gas
What are 4 assumptions about the Kinetic Molecular Theory of Gases?
- They have negligible molecular size
- They are point particles with only translational kinetic energy
- They have elastic collisions and constant velocity
- They don’t have any intermolecular forces
Explain why gases have negligible molecular size according to the Kinetic Molecular Theory of Gases.
- the actual size of a gas molecule is so small that it can be ignored when considering the overall volume of the gas
Explain why gases are point particles with translational energy according to the Kinetic Molecular Theory of Gases.
- they get their energy purely from motion through space, with no internal vibrational or rotational energies
Explain why gases have elastic collisions and constant velocity according to the Kinetic Molecular Theory of Gases
- there is no net loss of kinetic energy during collisions, meaning molecules will rebound without changing their speed
Explain why gases don’t have any intermolecular forces according to the Kinetic Molecular Theory of Gases
- gases do NOT exert attractive or repulsive forces on one another meaning they will move independently until they collide
How is the temperature and average kinetic energy related?
average kinetic energy and temperature are proportional to eachother
- when temperature increases, so does the average kinetic energy
TRUE OR FALSE: all gas molecules move at the same speed
FALSE: there is a distribution of speeds where some molecules move faster and others slower
What 3 factors influence gas pressure?
- The mass of each molecule
- The speed of each molecule
- The frequency of collisions
How does the mass of a molecule influence gas pressure?
heavier molecules contribute more to pressure because each collision will increase momentum
How does the speed of a molecule influence gas pressure?
faster moving molecules collide more frequently and with greater force, therefore increasing pressure
How do the frequency of collisions affect gas pressure?
the # of molecules and the volume of the container determine how often molecules collide with each other and the container walls.
MORE molecules and/or a SMALL volume with increase collisions and pressure.
What equation relates pressure to molecular properties?
P = 1/3 (N/V) (m)(u^2)
where p = pressure
N = # of molecules
V = volume of container
m = mass of one molecule
u^2 = mean-square speed
What is the Root-Mean-Sqaure (RMS) Speed?
the measure of the average speed of gas molecules
TRUE OR FALSE: lighter gases move FASTER than heavier ones at the same temperature
TRUE: because the RMS speed of 2 different gases is INVERSELY proportional to the square root of their molar masses
What is effusion?
the process at which gas molecules pass through a tiny opening from a region of high pressure to low pressure
TRUE OR FALSE: effusion typically occurs at low pressures
TRUE
What 3 factors affect effusion
- Molecular Mass
- Temperature
- Size of Pore/Hole
How does molecular mass affect effusion?
lighter molecules have faster effusion rates than heavier ones because they move faster at a set temperature
How does temperature affect effusion?
higher temperatures increase molecular speeds, therefore also increasing effusion rates
How does the size of pore/hole affect effusion?
smaller pores restrict larger molecules more effectively, increasing the rate of effusion
What is Graham’s Law?
states that the rate of effusion is inversely proportional to the square root of its molar mass
What is an enrichment factor?
ratio that compares how much one gas effuses vs the other based on their molar masses
