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CHEM1045 > Chapter 5 - Gases > Flashcards

Chapter 5 - Gases Flashcards

1
Q

Gas molecules are constantly in

A

Motion

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2
Q

As they move and strike the surface they ___ on the surface

A

Push (push = force)

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3
Q

The pressure of gas would be

A

The total amount of force extorted by gas molecules hitting the entire surface at any one instant

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4
Q

Pressure formula

A

Force / Area

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5
Q

Whenever there is a pressure difference, a gas will flow from an area of ___ pressure to an area of ___ pressure

A

High to Low

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6
Q

Differences in air pressure result in

A

Weather and wind patterns

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7
Q

The ___ in the atmosphere you climb, the ___ the atmospheric pressure is around you

A

Higher, Lower

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8
Q

If there’s a difference in pressure across the eardrum membrane, the membrane will be

A

Pushed out (popped eardrum)

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9
Q

What does the pressure of a gas depend on?

A
  • Number of gas particles in a given volume
  • Volume of the Container
  • Average Speed of the gas particles
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10
Q

Air pressure is measured with a

A

Barometer
• Column of mercury supported by air pressure
• Force of the air in the surface of the Mercury counter balances the force of gravity on the column of mercury

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11
Q

What happens to the height of the column of mercury in a mercury barometer as you climb to the top of a mountain?

A

The height of the column decreases because atmospheric pressure decreases with increasing altitude

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12
Q

Atmosphere (atm) =

1) millimeters of mercury (mmHg)
2) Torr (torr)

A

1) 760 mmHg

2) 760 torr

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13
Q

The pressure of a gas trapped in a container can be measured with an instrument called

A

Manometer

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14
Q

In a manometer, the difference in the liquid levels is a measure of the difference in

A

Pressure between the gas and the atmosphere

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15
Q

Boyle’s Law

A
  • Pressure of a gas is inversely proportional to its volume
  • As P increases, V decreases by the same factor
  • P x V = Constant
  • P1 x V1 = P2 x V2
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16
Q

Boyle’s Law and Diving

A

Because water is more dense than air, for each 10m you dive below the surface, the pressure on your lungs increases 1 atm.

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17
Q

If a driver holds her breath and rises to the surface quickly

A

She should exhale, to avoid the volume expanding by a factor of 3 which causes damage to internal organs

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18
Q

Charles’ Law

A
  • Volume is directly proportional to temperature.
  • As T increases, V also increases.
  • V = constant x T.
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19
Q

Charles’ Law and Absolute Zero

A

• If you plot volume vs. temperature for any gas at constant pressure, the points will all fall on a straight line.
• If the lines are extrapolated back to a volume of “0”, they all show the same temperature
(-273.15C) called Absolute Zero.

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20
Q

Avogadro’s Law

A
  • Volume is directly proportional to the number of gas molecules.
  • V = constant x n
  • Count number of gas molecules by moles
  • Equal volumes of gases contain equal numbers of molecules (the gas doesn’t matter)
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21
Q

Ideal Gas Law

A

• R is called the Gas Constant
• The value of R depends on the units of P and V
• (P)(V) / (n)(T) = R
OR PV = nRT

22
Q

What are the Standard Conditions?

A

Because the volume of a gas varies with pressure and temperature, chemists have agreed on a set of conditions to report our measurements so that comparison is easy

23
Q

Standard Conditions

A
  • STP
  • Standard pressure = 1 atm
  • Standard temperature = 273 K (0C)
24
Q

Molar Volume

A
  • Solving the ideal gas equation for the volume of 1 mil of gas at STP gives 22.4L
  • We call the volume of 1 mole of gas at STP molar volume
  • It is important to recognize that one mole measures of different gases have different masses even though they have the same volume
25
Q

Density at Standard Conditions

A
  • Density is the Ratio of Mass to Volume
  • Density of a gas is generally given in g/L
  • The volume of 1 mole at STP = 22.4L
  • Density = (Molar Mass, g) / 22.4L
26
Q

Density id directly proportional to

A

Molar Mass

27
Q

Molar Mass of a Gas

A
  • One of the methods chemists use to determine the molar mass of an unknown substance is to heat a weighed sample until it becomes a gas, measure the temperature, pressure, and volume, and use the ideal gas law
  • Molar Mass = Mass in grams / Moles
28
Q

Mixture of Gases

A
  • When gases are mixed together, their molecules behave independent of each other
  • Therefore, in certain application the mixture can be thought of as one gas
29
Q

The pressure of a single gas in a mixture of gases is called its

A

Partial pressure

30
Q

The sum of the partial pressures of all the gases in the mixture equals the Total Pressure

A

Dalton’s Law of Partial Pressures

31
Q

Kinetic-molecular theory says that

A

The gas molecules are negligibly small and don’t interact

32
Q

Because the gas molecules are not sticking together, each gas molecule contributes its own force to the total force on the side

A

Dalton’s Law and Pressure

33
Q

Gases in the same container have the same temperature, therefore

A

They have the same average kinetic energy

34
Q

If gases have different masses, the only way for them to have the same kinetic energy is to have

A

Different average velocities

35
Q

All the gas molecules in a sample can travel at different speeds. However, the distribution of speeds follows a statistical pattern called a

A

Boltzman Distribution

36
Q

As the absolute temperature increases,

A

The average velocity increases

37
Q

The average distance a molecule travels between collisions is called the

A

Mean Free Path

38
Q

As the pressure increases

A

The mean free path decreases

39
Q

The process of a collection of molecules spreading out from high concentration to low concentration is called

A

Diffusion

40
Q

The process by which a collection of molecules escapes through a small hole into vacuum is called

A

Effusion

41
Q

The rates of diffusion and effusion of a gas are both related to

A

It’s rms average velocity

42
Q

For two different gases at the same temperature, the ratio of their rates of effusion is given by an equation

A

Graham’s Law of Effusion

43
Q

Ideal gas laws assume

A
  • No attractions between gas molecules

* Gas molecules do not take up space (based on the kinetic-molecular theory)

44
Q

Real gases often do not behave like ideal gases at

A

High pressure or low temperature

45
Q

The ___ ___ makes the real volume larger than the ideal gas law would predict. the ___ ___ make the real pressure less than the ideal gas would predict.

A

Molecular Volume, Intermolecular Attractions

46
Q

____ modified the ideal gas equation to account for the molecular volume and intermolecular attractions

A

Van Der Waals Constant

47
Q

The ____ is the layer closest to the Earth’s surface (circular due to thermal currents.

A

Troposphere (weather)

48
Q

The ____ is the next layer up (less air mixing)

A

Stratosphere

49
Q

The boundary between the troposphere and stratosphere is called the

A

Tropopause

50
Q

The ___ ___ is a layer of high O3 concentration located in the stratosphere

A

Ozone Layer

CHEM1045 (7 decks)

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