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AP Chemistry > Unit 6- Gas Laws > Flashcards

Unit 6- Gas Laws Flashcards

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1
Q

Define Pressure.

A

Pressure is defined as a force applied over a given area; pressure is created by gases through collisions with an object.

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2
Q

What keeps the air that we breathe from blowing away as the earth spins on its axis?

A

The gravitational field of the earth keeps the air that we breathe from blowing away.

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3
Q

Why don’t gas molecules just sit on the surface of the earth?

A

The random motion of the gases prevent them from sitting on the surface of the earth; additionally, their collisions with molecules in their proximity prevent them from sitting on the surface of the earth.

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4
Q

Define Atmospheric Pressure.

A

Atmospheric pressure is defined as the force that is exerted by atmospheric gases in our proximity as they collide with one another at a specific elevation point.

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5
Q

What happens to atmospheric pressure as you travel to higher altitudes?

A

At higher altitudes, the atmospheric pressure decreases.

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6
Q

What is the movement of gases in relation to pressure?

A

They move from an area of high pressure to an area of low pressure.

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7
Q

How is a liquid “pushed” up a straw?

A

As gases are inhaled, the pressure in the straw is lowered; thus, the atmospheric pressure pushes the liquid through the straw.

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8
Q

Why does a potato chip bag appear to inflate as you go skiing in the mountains?

A

As you go higher in altitude, the pressure on the outside lowers; meanwhile, the pressure inside the bag stays the same.

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9
Q

Why is soda can “crushed” when you place a small quantity of water in the bottom of it, boil the water so that steam is visibly exiting the can, and then flip the can over into a tub of ice water?

A

The hot gases in the can suddenly cool which in turn lower the pressure; meanwhile, the outside pressure is greater which in turn crushes the can.

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10
Q

How does a very simple barometer composed of an inverted tube of mercury in a dish of excess mercury work?

A

There is a vacuum (a space devoid of matter) in the inverted tube; so, the atmospheric pressure pushes the mercury up the inverted tube.

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11
Q

Why does a helium balloon pop as it disappears from sight?

A

As the pressure decreases, the balloon expands to the point where the material of the balloon is eradicated.

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12
Q

Why must a scuba diver use high pressure air in order to properly breathe deep in the ocean?

A

The pressure in the water prevents the two lungs from expanding enough to be able to breathe; in order to combat this, high pressure is needed.

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13
Q

Why do air bubbles form in a scuba diver’s body if they surface too fast?

A

There is high pressure in the dissolved air; thus, as a diver gets closer to the surface, pressure decreases which allows for air to precipitate.

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14
Q

Define an Ideal Gas.

A

An ideal gas is defined as a gas with an insignificant amount of particle volume and no IMFs.

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15
Q

Particles are very _____ relative to distances between them; consequently, the _____ of the individual particles can be assumed to be negligible.

A

Small, Volume

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16
Q

Particles are in constant _____ ; pressure is a result of the _____.

A

Motion, collisions of the gases with the walls of the container.

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17
Q

Particles are assumed to have _____ interaction with one another.

A

Zero/ Insignificant

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18
Q

The average kinetic energy of the particles is directly proportional to the _____.

A

Temperature

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19
Q

List all of the Gas Laws.

A

Ideal Gas Law, Avogadro’s Law, Gay-Lussac’s Law, Boyle’s Law, Charles’ Law (IAGBC)

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20
Q

For all of the Gas Laws, the temperature must be expressed in _____.

A

Kelvin (K).

21
Q

How is Celsius converted into Kelvin?

A

C+ 273.15= K

22
Q

Explain everything about the Ideal Gas Law.

A

PV= nRT; The Ideal Gas Law defines the conditions of a gas at a particular time; given 3 variables, find the fourth. Pressure is in atm, Volume is in Liters, n is moles, R is the Ideal Gas Law Constant which is 0.08206 Latm/ (mol.K); Temperature is in Kelvin

23
Q

Explain everything about Avogadro’s Law.

A

Avogadro’s Law states that equal volumes of gases at the same temperature and pressure contain the same number of moles. V1/n1= V2/n2; KMT: Volume depends on the number of particles present. If you increase the number of particles, you increase the volume.

24
Q

Explain everything about Gay-Lussac’s Law.

A

Gay-Lussac’s Law relates pressure and temperature at constant volume and number of moles. P1/T1= P2/T2; KMT: The speed of particles increases. The particles hit the walls of their container with more force and frequency. As a result, pressure increases.

25
Q

Explain everything about Charles’ Law.

A

Charles’ Law states that the volume of a gas at constant pressure increases linearly with temperature. V1/T1= V2/T2; KMT: if temperature is increased, molecules speed up and collide more frequently with the walls of their container. If the container is expandable, the volume increases to maintain constant pressure.

26
Q

Explain everything about Boyle’s Law.

A

Boyle’s Law states that the volume of a gas is inversely proportional at constant temperature and moles. P1V1=P2V2; KMT: If the volume of a gas is decreased, gas particles will hit the walls of their container more frequently- this leads to an increase in pressure.

27
Q

What is the Combined Gas Law?

A

P1V1/n1T1= P2V2/n2T2

28
Q

Give the equivalents of pressure.

A

1 atm= 760mmHg= 760 torr= 101.3 kPa= 14.7 psi= 1.01 bar.

29
Q

List the four principles of the Kinetic Molecular Theory.

A
  1. Particles are very small relative to distances between them. Consequently, the volume of the individual particles can be assumed to be negligible. 2. Particles are in constant motion. Pressure is a result of the collision of particles with the walls of their container. 3. Particles are assumed to have no interaction with one another. 4. The average kinetic energy of the particles is directly proportional to the temperature.
30
Q

Give the relationship between Density and Molar Mass with respect to the Ideal Gas Law.

A

PMM/RT=D ; DRT/P=MM

31
Q

What are the general characteristics of gases?

A

A gas uniformly fills any container, is easily compressed, and mixes completely with any other gas. One of the most obvious properties of a gas is that it exerts pressure on its surroundings.

32
Q

How does a manometer measure the pressure of a gas?

A

A manometer operates based on the difference in the pressures of the gases.

33
Q

What is Dalton’s Law of Partial Pressure?

A

The total pressure of a system is the sum of each individual gas pressure. P Total= P1+ P2+ P3…

34
Q

Why does Dalton’s Law of Partial Pressures work? What is it about gases that allows the relationship to hold true?

A

Because the total number of moles of particles are important, not the identity or the composition of the gas particles. The fact that the pressure exerted by an ideal gas is not affected by the identity (composition) of the gas particles reveals 2 things about gases: (1) the volume of the gas particles must not be important and (2) the forces among the particles must not be important.

35
Q

What is a mole fraction?

A

Mole fraction is defined as the ratio of the number of moles of a given component in a mixture to the total number of moles in the mixture; XA= nA/ nTotal; Mole fractions should always add up to 1

36
Q

How can mole fractions be used to find the partial pressure of a gas? Write an equation.

A

XA. PTotal= PA so PA/PTotal=XA

37
Q

Write an equation that relates Kelvin temperature to average kinetic energy. What is temperature?

A

KEavg=3/2RT; the Kelvin temperature is an index of the random motions of the particles of a gas with higher temperature; KEavg is in units of J/mol. R= 8.3145J/molK

38
Q

Write an equation for average speed (urms). Explain the units used in the equation.

A

urms= (3RT/M)½ ; R= 8.3145J/molK ; T= Temperature in Kelvin; M= Molar Mass in kg/mol. urms should be in units of meters per second. m/s

39
Q

Explain the difference between kinetic energy and speed.

A

Speed is defined as the distance travelled in unit time whereas kinetic energy is defined as the ability to do work; also, the relationship between the two is direct: a modest increase in speed can cause a large increase in kinetic energy.

40
Q

If you have two gases at the same temperature, which one would be moving with a higher average speed?

A

The gas that contains lighter particles (in terms of mass) will be moving with a higher average speed.

41
Q

What is mean free path and what affects it?

A

Mean free path is defined as the average distance a particle travels between collisions in a particular gas sample; it’s typically a very small distance. The mean free path is affected by density; as gas density increases, the molecules become closer to one another. Therefore, they are more likely to run into each other, so the mean free path decreases.

42
Q

How does velocity distribution change with temperature?

A

As the temperature is increased, the curve peak moves toward higher values and the range of velocities becomes much larger. Because kinetic energy increases with temperature, it makes sense that the peak of the curves should move to higher values as the temperature of the gas is increased.

43
Q

What is effusion?

A

Effusion is defined as the movement of gases through an opening from high pressure to low pressure.

44
Q

What is diffusion?

A

Diffusion is defined as the mixing of gases.

45
Q

What is an important thing to note about heavy gases and light gases when it comes to effusion and diffusion?

A

At the same temperature and pressure, heavy gases effuse (or diffuse) slower than light gases.

46
Q

What is the equation to relate the rate of effusion & the rate of diffusion of two separate gases?

A

rGas A/rGas B = (MGas B)½/(MGas A)½

47
Q

What two values need to be corrected for a real gas? Why?

A

Volume/ Attractions that occur among the particles in a real gas. Volume: the volume available to a given particle in a real gas is less than the volume of the container because the gases themselves take some of the space. Attraction: when gas particles come close together, attractive forces occur, which cause the particles to hit the wall very slightly less often than they would in the absence of these interactions.

48
Q

Explain how the Ideal Gas Law changes for real gases?

A

A real gas typically exhibits behavior that is closest to ideal behavior at low pressures and high temperatures.

AP Chemistry (8 decks)

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