5.3.2 Effusion and Diffusion Flashcards Preview

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Flashcards in 5.3.2 Effusion and Diffusion Deck (12)
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1
Q

effusion and diffusion

A
  • Effusion is the process by which particles of a gas escape their container through a very small hole.
  • Diffusion is the process by which particles travel through molecules of a different substance or a semipermeable membrane.
2
Q

note

A
  • Effusion is the process by which particles of a gas escape their container through a very small hole.
  • The rate of effusion is governed by Graham’s law of effusion. Graham’s law of effusion states that the ratio of the rates of effusion of two gases is equal to the ratio of their root-mean-square speeds. Since the root-mean-square speed is the square root of 3RT/M, Graham’s law of effusion can be expressed in terms of the molecular masses (M) of the two gases.
  • By Graham’s law of effusion, lighter particles have higher root-mean-square speeds, and therefore diffuse faster. This is why helium balloons deflate more quickly than air-filled balloons.
  • Diffusion is the process by which particles travel through molecules of different substances or a semipermeable membrane. As with effusion, lighter particles diffuse more rapidly than heavier particles.
  • Ammonia (NH 3 ), for example, is lighter than hydrogen
    chloride (HCl). When placed at opposite ends of a tube, the NH 3 molecules diffuse faster than the HCl molecules, and thus travel further in the same amount of time.
3
Q

Which of the following shows the correct rate ratio for Graham’s law of effusion?

A

umsgas1 / umsgas2 = sqrt 3(R)(T)/Mgas1 / 3(R)(T)/Mgas2 = sqrt Mgas2/Mgas1

4
Q

Which of the following statements about diffusion is not correct?

A

Diffusion is a process in which a gas passes through a small, pinhole opening into a vacuum.

5
Q

In the diffusion demonstration involving HCl gas and NH3 gas traveling from opposite ends through a tube, a chemical event occurred. The result was the formation of a solid precipitate closer to the HCl end than the NH3 end. Why did this happen?

A

This occurred because the NH3 gas traveled faster than the HCl gas because the NH3 molecules are lighter. Therefore, they met at a point closer to the HCl end. At that point, the chemical event occurred.

6
Q

The ratio of the rate of effusion of gas 2 to the rate of effusion of gas 1 is 0.22. If the molar mass of gas 1 (Mgas 1 ) is 3.79 g / mol, what is the molar mass of gas 2?

A

78 g / mol

7
Q

Graham’s Law of effusion compares the rates effusion of two different gases, and how it relates to its molar masses. The average speed (m) of a gas molecule is directly related to the rate of effusion and is written as,
R = gas constant
T = absolute temperature
M = molar mass of the gas
u = sqrt 3RT/M
Under constant temperature, which of the following is equal to the ratio?

A

sqrt Mgas2 / Mgas1

8
Q

Which of the following statements related to Graham’s law of effusion is not correct?

A

The ratio that you get from the Graham’s law of effusion equation has units of g / mol.

9
Q

Which of the following best defines effusion?

A

Effusion is the movement of gas particles through a pinhole into a vacuum.

10
Q

The molar mass of gas 1 is 5.08 g / mol. If the rate of effusion of gas 1 is 3.57 times faster than the rate of effusion of gas 2, what is the molar mass of gas 2?

A

64.7 g / mol

11
Q

We have discovered that Graham’s law of effusion allows us to compare the two root mean square speeds of two gases by comparing the molar masses, M. You can use the following equation to find the ratio: urmsGas1/urmsGas2 = sqrt M(gas2)/M(gas1). Which of the following statements is correct, based on this relationship between the two gases?

A

If the molar mass of gas 2 is greater than the molar mass of gas 1, the value of the ratio of the rate of effusion of gas 1 to that of gas 2 is greater than 1.

12
Q

Which of the following statements is not true?

A

Diffusion and effusion both involve the movement of a gas into a vacuum.

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