Chem - Ch 13.1, 14 Flashcards
What are the 3 assumptions of kinetic theory as it applies to gases
particles in a gas are considered to be small hard spheres with an insignificant volume
motion of particles in a gas is rapid, constant, and random
all collisions between particles in a gas are perfectly elastic
how do the particles of a gas travel
in straight-line paths until they collide with another particle or another object
what is pressure
force per area
what causes gas pressure
billions of rapidly moving particles in a gas simultaneously colliding with an object
what is a vacuum
empty space
what is a barometer
a device used to measure atmospheric pressure
how does a barometer work
there is a mercury column in a tube. the height of the mercury column depends on the pressure exerted by particles in the air colliding with the surface of mercury in the dish
what is the relationship between kinetic energy and kelvin temperature
the kelvin temp of a substance is directly proportional to the average kinetic energy of the particles of a substance
what is compressibility
a measure of how much the volume of matter decreases under pressure
why are gases easier to compress than liquids or solids
because of the space between the particles in a gas
why do airbags work
the compression of the gas inside the airbag absorbs the energy of the impact
what are the three factors that affect gas pressure
the amount of gas
the volume of gas
the temperature
what is an example of the effect of the amount of gas on pressure
if you add more air into a raft, the pressure inside the raft will increase
what is an example of the effect of the volume of gas on pressure
when a car piston forces gas into a smaller volume, the pressure increases
what is an example of the effect of the temperature on pressure
a hot potato chip bag will bulge at the seams because and increase in temp causes an increase in pressure
how are pressure and volume related
inversely proportional
how are temperature and volume related
directly proportional
what is so special about -273 degrees C
it is the same as 0 K
why do you have to use K when solving gas law problems
it is not a direct relationship if temp is expressed in celsius
Kelvin is an absolute temperature scale that starts at 0
how are pressure and temperature related
directly proportional
how do pressure cookers reduce cooking time
they increase the pressure of the steam which raises the temperature of it which causes the food to cook faster
what is the combined gas law
PV/nT = PV/nT
what has to be constant throughout the combined gas law
units
what is the ideal gas law
PV = nRT
Under what conditions are real gases most likely to differ from ideal gases
At low temps and high pressures
Under what conditions are real gases most likely to differ from ideal gases
At low temps and high pressures
How is the total pressure of a gas mixture related to the partial pressures of the component gases
In a mixture of gases, the total pressure is the sum of the partial pressures of thegases
What does gas pressure depend on
The number or particles in a given volume and the average kinetic energy of those particles
How does Dalton’s law of partial pressures hold true
Each component gas exerts it’s own pressure independent of the pressure exerted by the other gases
Does the kind of particle affect gas pressure
No, amount of gas and their avg KE does
If the temperature of a fixed quantity of gas decreases, and the pressure remains unchanged, what happens to the volume
It decreases
If the temperature of a fixed quantity and a fixed volume of gas changes, what also changes?
Pressure
If the volume of a container of gas is reduced, what will happen to the pressure inside the container
The pressure will increase
What happens to the pressure of a gas inside a rigid container if the temp of the gas decreases?
Pressure decreases
If a balloon is heated, what happens to the volume of the air in the balloon if pressure is constant
It increases
What is the combined gas law
PV/nT
What is diffusion
The tendency of molecules to move towards ares of lower concentration until the concentration is uniform throughout
What is effusion
When gas escapes from a tiny hole in its container
What is Graham’s law of effusion
The rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass
why did the can crush experiment work
the particles were heated up, and when it go put into the cold water, they cooled down so the internal pressure decreased causing the external pressure to crush it
Increasing the volume of a given amount of gas at a constant temperature causes the pressure to decrease because why?
The molecules are striking a larger area w the same force
Why does 19.0 grams of fluorine gas at stp contain the same number of molecules as 1/2 a mole of oxygen at stp
Because 19.0 of fluorine is 1/2 a mole of fluorine and 1/2 a mole of anything is always the same amount of molecules
In class we put a marshmallow peep into a vacuum chamber & removed some of the air in the chamber. What happened to the marshmallow and why?
The marshmallow expanded as we continued taking air out of the chamber. As we removed air from the chamber, this decreased the pressure inside bc n and p are directly proportional. This decreased the external pressure on the peep. The volume of the peep increased in order to decrease it’s internal pressure (since v and p are inversely proportional) so that the external and internal pressures could be balanced.
You have two containers, each holding 1 mole of Xenon gas at 15°C. Container A has a volume of 3.0 L and container B has a volume of 1.0 L. How does the average kinetic energy of the xenon atoms compare between the two containers?
Same in both containers bc avg kinetic energy if particles is directly proportional to their kelvin temp and they both have the same kelvin temp since they are in the same environment
You have two containers, each holding 1 mole of Xenon gas at 15°C. Container A has a volume of 3.0 L and container B has a volume of 1.0 L. Compare the forces with which the xenon atoms collide with the sides of each container
Same force bc the temp is the same, so their kinetic energies are the same, and they both have the same amount of molecules, so they are moving with the same speed/force
You have two containers, each holding 1 mole of Xenon gas at 15°C. Container A has a volume of 3.0 L and container B has a volume of 1.0 L. Compare the pressures of the 2 xenon samples
Pressure in container A is less than that of container b bc CA has a bigger volume CB, and when n and t are constant, pressure and volume are inversely proportional
