Unit 6- Gas Laws

Question 1

Define Pressure.

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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.

Question 4

Define Atmospheric Pressure.

Answer 4

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.

Question 5

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

Answer 5

At higher altitudes, the atmospheric pressure decreases.

Question 6

What is the movement of gases in relation to pressure?

Answer 6

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

Question 7

How is a liquid “pushed” up a straw?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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?

Answer 9

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.

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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.

Question 13

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

Answer 13

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.

Question 14

Define an Ideal Gas.

Answer 14

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

Question 15

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

Answer 15

Small, Volume

Question 16

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

Answer 16

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

Question 17

Particles are assumed to have _____ interaction with one another.

Answer 17

Zero/ Insignificant

Question 18

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

Answer 18

Temperature

Question 19

List all of the Gas Laws.

Answer 19

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

Question 20

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

Answer 20

Kelvin (K).

Question 21

How is Celsius converted into Kelvin?

Answer 21

C+ 273.15= K

Question 22

Explain everything about the Ideal Gas Law.

Answer 22

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

Question 23

Explain everything about Avogadro’s Law.

Answer 23

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.

Question 24

Explain everything about Gay-Lussac’s Law.

Answer 24

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.

Question 25

Explain everything about Charles' Law.

Answer 25

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.

Question 26

Explain everything about Boyle's Law.

Answer 26

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.

Question 27

What is the Combined Gas Law?

Answer 27

P1V1/n1T1= P2V2/n2T2

Question 28

Give the equivalents of pressure.

Answer 28

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

Question 29

List the four principles of the Kinetic Molecular Theory.

Answer 29

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.

Question 30

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

Answer 30

PMM/RT=D ; DRT/P=MM

Question 31

What are the general characteristics of gases?

Answer 31

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.

Question 32

How does a manometer measure the pressure of a gas?

Answer 32

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

Question 33

What is Dalton's Law of Partial Pressure?

Answer 33

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

Question 34

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

Answer 34

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.

Question 35

What is a mole fraction?

Answer 35

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

Question 36

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

Answer 36

XA. PTotal= PA so PA/PTotal=XA

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

Explain the difference between kinetic energy and speed.

Answer 39

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.

Question 40

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

Answer 40

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

Question 41

What is mean free path and what affects it?

Answer 41

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.

Question 42

How does velocity distribution change with temperature?

Answer 42

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.

Question 43

What is effusion?

Answer 43

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

Question 44

What is diffusion?

Answer 44

Diffusion is defined as the mixing of gases.

Question 45

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

Answer 45

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

Question 46

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

Answer 46

rGas A/rGas B = (MGas B)½/(MGas A)½

Question 47

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

Answer 47

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.

Question 48

Explain how the Ideal Gas Law changes for real gases?

Answer 48

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