Question

(a) The density of the interstellar gas, mainly hydrogen (2 g/mol), is approximately one molecule (2 g/mol).
per cubic centimeter. If the molar diameter is 10-10 m, what is the average free path? What is the
the collision frequency for a hydrogen molecule if the temperature is 3 K?

(b) It has been seen that for diffusion, the distance travelled by a molecule is proportional to the root of the molecule.
square of the number n of collisions, i.e. the total distance travelled d = pn. The time required, on the other hand,
is proportional to the number of collisions. Estimate the time required for a molecule of "air" (29
g/mol) in a room at atmospheric pressure and 20◦C moves at a distance of 5 m.

Answer 1

(1)

(2)