**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/m
^{3} - B
molecules/m
^{3} - C
molecules/m
^{3} - D
molecules/m
^{3} - E
molecules/m
^{3}

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

- A
mol/m
^{3} - B
mol/m
^{3} - C
mol/m
^{3} - D
mol/m
^{3} - E
mol/m
^{3}

**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