Kinetic theory of Gas Molecules Flashcards

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1
Q

Explain Boyle’s Law

A
  • The pressure of a gas at constant temperature is increased by reducing its volume.
  • The gas molecules travel less distance between impacts at the wall due to the reduced volume.
  • Therefore there are more impacts per second.
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2
Q

Explain the pressure law

A
  • The pressure of a gas at constant volume is increased by raising its temperature.
  • Molecules travel faster so mean kinetic energy of molecules increases
  • Momentum of molecules increases
  • Impacts are harder and more frequent
  • Each collision transfers more momentum
  • More force per unit area on container walls
  • So the pressure increases.
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3
Q

Molecules in a gas have a spread of speeds.

A
  • In a collision the speed of the molecules will change.
  • If temperature does not change, distribution will stay the same.
  • If the temperature of a gas is raised, its molecule move faster, on average. The root mean square speed of the molecules increases.
  • The distribution curve become broader and flatter because the greater temperature, the more molecules there are moving at higher speeds.
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4
Q

What is the root mean square speed, crms.

A

Square root of the mean value of the square of the molecular speeds of the molecules of a gas.

Crms = (c12+c22+c32…+cN2/N)½

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5
Q

What is the kinetic theory equation?

A

pV = 1/3Nm(crms)<span>2</span>

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6
Q

Assumptions of the kinetic theory equation

A
  • All particles are identical / have same mass
  • The collisions they undergo with each other and with the container of the surface are elastic collisions.
  • Intermolecular forces are negligible except during collisions. If the forces are not negligible the force of the impact on the container walls would be reduced.
  • Volume of molecules is negligible (point molecules) compared to volume of container/gas
  • Time of collisions is negligible (duration of collision / time between collisions)
  • They move about in continual random motion (range of speeds + no preferred direction of movement)
  • Large no of molecules present / statistical laws apply
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7
Q

Kinetic energy of the molecules of an ideal gas:

A

Mean kinetic energy of a molecule of an ideal gas= 3/2kt

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8
Q

Total kinetic energy for one mole =

A

NAx(3/2)kT = 3/2RT

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9
Q

Total KE for n moles =

A

3/2nRT

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