# Worksheet: Mean Free Path of Gas Molecules

Q1:

The mean free path for methane at a temperature of 273 K and a pressure of Pa is m. Find the effective radius of the methane molecule.

• A m
• B m
• C m
• D m
• E m

Q2:

The mean free path for helium at a certain temperature and pressure is m . Use a value of m for the radius of a helium atom.

What is the density of helium under these conditions in molecules per cubic meter?

• A molecules/m3
• B molecules/m3
• C molecules/m3
• D molecules/m3
• E molecules/m3

What is the density of helium under these conditions in moles per cubic meter?

• A mol/m3
• B mol/m3
• C mol/m3
• D mol/m3
• E mol/m3

Q3:

For the equations of hydrodynamics to apply to a highly compressible fluid, the mean free path must be much less than the linear size of a volume , where is a small volume of fluid. For air in the stratosphere at a temperature of 220 K and a pressure of 5.8 kPa, determine the value of that is 100 times greater than the mean free path of molecules in the air. Use a value of m as the effective radius of the molecules in air.

Q4:

Find the total number of collisions between molecules in 1.70 s interval within 1.25 L of nitrogen gas that is at a temperature of and at a pressure of 1.00 atm. Use m as the effective radius of a nitrogen molecule and use a value of 28.0 g/mol for the molar mass of nitrogen. Consider that each collision involves two molecules, therefore if a molecule collides with a molecule during a time interval, the collision of either molecule or molecule is counted, but not both.

• A
• B
• C
• D
• E