Even though gas particles may travel at speeds of hundreds of meters per second, they do not move in a straight line for long. At room temperature, a molecule may collide billions of times each second, changing its direction with each collision.
The mean free path is the average distance a gas molecule travels between collisions. It generally increases as pressure decreases: at lower pressure, there are fewer particles in a given volume, so a molecule can travel farther before colliding. A molecule's mean free path is typically hundreds of times its diameter.
All flashcards
What is mean free path?
The average distance a gas particle travels between successive collisions; it generally increases as pressure decreases.
What is diffusion?
The dispersal of particles through space in response to concentration differences, producing net movement from higher to lower concentration.
What is effusion?
The escape of gas molecules through a tiny opening into a region of lower pressure.
What does Graham’s law predict?
At the same temperature, a gas’s effusion rate is inversely proportional to the square root of its molar mass.
Which factors influence diffusion rate?
Temperature, molar mass, concentration gradient, available surface area, and travel distance.
Quiz questions
What is the mean free path of a gas molecule?Answer: The average distance it travels between successive collisions.
How does effusion differ from diffusion?Answer: Effusion is gas escaping through a tiny opening; diffusion is particle dispersal due to concentration differences.
At the same temperature, how does a gas’s effusion rate depend on its molar mass according to Graham’s law?Answer: It is inversely proportional to the square root of molar mass.
For equal amounts of two gases under the same conditions, what is true of effusion time?Answer: The gas with the greater effusion rate takes less time.
Why did gaseous-diffusion uranium enrichment use many stages in a cascade?Answer: Each barrier slightly enriched the gas in uranium-235, so many stages increased the enrichment gradually.
Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.