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Chemistry > Chapter 6 - Gases > Flashcards

Chapter 6 - Gases Flashcards

1
Q

What are the 7 main proportie of gas?

A
  • No fixed volume, expand to fill their container
  • No fixed shape, take the shape of container
  • Highly compressible
  • Mix completely with other gases
  • Exert pressure on their surroundings
  • Very low density
  • Fluid, flow from high to low pressure
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2
Q

What is pressure?

A
  • Force per unit area
  • The SI unit of pressure is the pascal (PA)
    • 1 Pa = 1 N/m^2 = 1 kg/(m*s^2)
  • Torrs and standard atmospheres (atm) are not SI
    units
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3
Q

What is a barometer?

A
  • Barometers measure atmospheric pressure
  • The first barometer was a tube of Hg inverted
    into a bowl
  • At sea level, the Hg column is 760 mm
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4
Q

What is a manometer?

A

Manometers measure gas pressure inside a flask relative to atmospheric pressure

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5
Q

What is Boyle’s Law?

A

At constant temperature and moles the pressure and volume of a gas are inversely proportional
- PV = k
- P1V1 = P2V2
- Gas pressure is a result of the particles striking
their container. As pressure increases, the
particles collide with the container more often

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6
Q

What are ideal gases?

A

They strictly obey all gas laws
- volumeless
- strike each other with elastic collisions (like pool
balls)
- have no attraction to one another

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7
Q

What are real gases?

A

They best obey gas laws at low pressures and high temperatures
- Low P: the particles’ volume is less significant
- High T: high KE avg makes collisions more elastic

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8
Q

What is Charles’ Law?

A
  • At constant pressure and moles, volume and
    temperature are directly proportional
  • Like all matter, gases expand when heated
  • Sealed cylinders with pistons and tied balloons
    demonstrate this law because P and n are
    constant
  • V = bT
  • V1/T1 = V2/T2
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9
Q

What is Avogadro’s Law?

A
  • V = an
  • V1/n1 = V2/n2
  • Inflating a balloon or adding gas to a cylinder
    with a moveable piston demonstrates
    Avogadro’s Law
  • For these objects (at constant P and T) adding
    more moles of gas increases volume
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10
Q

What is the Ideal Gas Law?

A
  • The behavior of a gas is governed by four
    variables, any of which can be calculated if the
    other three are known
  • PV = nRT
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11
Q

What is R?

A

The universal gas constant
- R = 0.08206 Latm/Kmol

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12
Q

what is STP?

A

Standard temperature and pressure, 0C and 1 atm

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13
Q

What is molar volume?

A
  • The volume of one mol of a gas
  • The molar volume of an ideal gas at STP is 22.42
    L
  • V = 1 mol0.08206273.15K / 1 atm = 22.42 L
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14
Q

How can molar mass and density be calculated?

A

They can be calculated from PV = nRT
- PV = mass/molar massRT
- molar mass = mass/PVRT
- d(density) = mass/V
- molar mass = dRT/P

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15
Q

What is Dalton’s Law?

A
  • For gas mixtures, the total pressure is the sum of
    the pressures each gas would exert by itself
  • Ptotal = P1 + P2 + P3 + …
  • P1/Ptotal = n1/n total
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16
Q

What does a gas always contain when it is collected over water?

A

It always contains a small amount of water vapor
- Subtract the vapor pressure of water from the
total pressure

17
Q

What is kinetic energy?

A
  • Gas particles frequently collide and exchange
    kinetic energy
  • A sample of gas at a given temperature has
    particles with a wide range of velocities
  • At higher T, these ranges become very broad
18
Q

What is the relationship between temperature and kinetic energy?

A
  • Temperature is a measure of average kinetic
    energy
  • This equation provides the KE avg of a mole of gas particles at a given temperature
  • KE ave = 3/2*RT
19
Q

What is root mean square velocity?

A
  • u rms is the average speed of particles in a
    sample of gas
  • units are in m/s
  • u rms = sqrt(3RT/M*M)
  • MM = molar mass in kg
  • the kinetic energy of an object in motion is its
    mass times its velocity squared
  • average kinetic energy is directly proportional to
    Kelvin temperature
20
Q

What is diffusion?

A

The mixing of gases

21
Q

What is effusion?

A

Movement of a gas through a pinhole into an evacuated chamber

22
Q

What is Graham’s law of effusion?

A
  • At the same temperature and pressure, the
    relative rates of effusion of two gases are given
    by the equation
  • effusion rate for gas 1 / effusion rate for gas 2
    = sqrt(MM2) / sqet(MM1)
  • Lower molar mass, lighter gas particles, higher
    velocities, faster effusion
23
Q

What is van der Waals equation?

A
  • The ideal gas law was adjusted to the van der
    Waals equation to describe real gas behavior
    more accurately
  • P + a(n/V)2 * (V - nb) = nRT
  • P corrected for intermolecular forces
  • V corrected for gas volume
  • a accounts for interactions among gas particles
    • gases with weak intermolecular forces have
      low values of a
  • b subtracts the volume of gas molecules
    themselves
    - generally increases with the size of the gas
    particle

Chemistry (9 decks)

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