CHEM357 Lecture Notes - Lecture 6: Mean Free Path

• School: University of Waterloo
• Department: Chemistry
• Course: CHEM357
• Professor: Elizabeth Meiering

Document Summary

Derivations: collisions between molecules and mean free path. Consider n identical molecules in volume v, with average speed, . (i) assume that molecule a moves, but all others are stationary; also assume a is a sphere, diameter = d. Then z = ( ) (n/v) z = number of coll/s of a with other molecules = (vol swept in 1 s) (number of molecules per cm3). (ii) but the molecules are not stationary; they are moving randomly. , the relative speed at which a approaches another molecule with which it will collide. Z = 2 n / v = Total number of collisions between all molecules in 1 cm3 of a gas (z). Total number of collisions, z, might seem to be z (n/v) Z = (1/2) z (n/v) The mean free path, l, is the average distance a molecule travels between collisions. In 1 s, a molecule travels cm and has z collisions. u.