Rate of Diffusion of gas into another gas By Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP Kingwood College Respiratory Care Department

Rate of diffusion of gas through another gas is dependent on several factors. Directly proportional to: –gradient –temperature –cross sectional Inversely proportional to: – Molecular weight –distant

Remember: we are not talking about if a gas can diffuse or not; we are discussing the rate or speed at which a gas can diffusion into another gas.

Directly proportional to: gradient 100% N2 3% N2 These gases will diffuse quickly because there is such a huge gradient between 100% and 3%.

Directly proportional to: temperature As the temperature rises, the molecules bounce faster

Directly proportional to: temperature Because they bounce faster, they move faster into the new area; diffusion is faster

Directly proportional to: cross sectional Look at the size of these two doors; it is clear that once it is open, more molecules can enter the larger doorway than the smaller one

Directly proportional to: cross sectional the larger the cross section, the faster the gas can diffuse into this area

Inversely proportional to: Molecular weight The more dense molecule such as the ones at the top will not diffuse as quickly as the smaller molecules. Think of a rabbit racing with a bear through the woods. The rabbit can dart in and out of the forest quicker than the bear can lumber along

Inversely proportional to: distant The gas in the larger container will diffusion slower than the gas in the smaller container because the same number of molecules have to traverse more distance