Why gases flow through small hole

The process is one of diffusion because the other side of the barrier is not evacuated. The UF 6 molecules have a higher average speed and diffuse through the barrier a little faster than the heavier UF 6 molecules. The gas that has passed through the barrier is slightly enriched in UF 6 and the residual gas is slightly depleted.

The small difference in molecular weights between UF 6 and UF 6 only about 0. But by connecting many diffusers in a sequence of stages called a cascade , the desired level of enrichment can be attained. Although the theory is simple, this required surmounting many daunting technical challenges to make it work in practice. The barrier must have tiny, uniform holes about 10 —6 cm in diameter and be porous enough to produce high flow rates.

All materials the barrier, tubing, surface coatings, lubricants, and gaskets need to be able to contain, but not react with, the highly reactive and corrosive UF 6. Because gaseous diffusion plants require very large amounts of energy to compress the gas to the high pressures required and drive it through the diffuser cascade, to remove the heat produced during compression, and so on , it is now being replaced by gas centrifuge technology, which requires far less energy.

A current hot political issue is how to deny this technology to Iran, to prevent it from producing enough enriched uranium for them to use to make nuclear weapons. Gaseous atoms and molecules move freely and randomly through space. Diffusion is the process whereby gaseous atoms and molecules are transferred from regions of relatively high concentration to regions of relatively low concentration.

Effusion is a similar process in which gaseous species pass from a container to a vacuum through very small orifices. At approximately what distance from the ammonia moistened plug does this occur? Effusion can be defined as the process by which a gas escapes through a pinhole into a vacuum.

Both A and B are in the same container at the same temperature, and therefore will have the same kinetic energy:. This book is Creative Commons Attribution License 4. Skip to Content Go to accessibility page. Chemistry 2e 9. My highlights. Table of contents. Answer Key. Figure 9. The lighter gas, H 2 , passes through the opening faster than O 2 , so just after the stopcock is opened, more H 2 molecules move to the O 2 side than O 2 molecules move to the H 2 side.

When this process is restricted to passage of molecules through very small openings in a physical barrier, the process is called effusion. The right-side photograph shows the balloons approximately 12 hours after being filled, at which time the helium balloon has become noticeably more deflated than the argon balloon, due to the greater effusion rate of the lighter helium gas.

Effusion Time Calculations It takes s for 4. Under the same conditions, how long will it take 4. Solution It is important to resist the temptation to use the times directly, and to remember how rate relates to time as well as how it relates to mass.

Note that this answer is reasonable: Since Ne is lighter than Xe, the effusion rate for Ne will be larger than that for Xe, which means the time of effusion for Ne will be smaller than that for Xe. Check Your Learning A party balloon filled with helium deflates to of its original volume in 8. Finally, here is one more example showing how to calculate molar mass from effusion rate data.

What is the molar mass of the unknown gas? Can you make a reasonable guess as to its identity? Check Your Learning Hydrogen gas effuses through a porous container 8. Estimate the molar mass of the unknown gas. Gaseous diffusion has been used to produce enriched uranium for use in nuclear power plants and weapons. Naturally occurring uranium contains only 0. In a gaseous diffusion enrichment plant, uranium hexafluoride UF 6 , the only uranium compound that is volatile enough to work is slowly pumped through large cylindrical vessels called diffusers, which contain porous barriers with microscopic openings.

The process is one of diffusion because the other side of the barrier is not evacuated. The UF 6 molecules have a higher average speed and diffuse through the barrier a little faster than the heavier UF 6 molecules.

The gas that has passed through the barrier is slightly enriched in UF 6 and the residual gas is slightly depleted. The small difference in molecular weights between UF 6 and UF 6 only about 0.

But by connecting many diffusers in a sequence of stages called a cascade , the desired level of enrichment can be attained. Although the theory is simple, this required surmounting many daunting technical challenges to make it work in practice. The barrier must have tiny, uniform holes about 10 —6 cm in diameter and be porous enough to produce high flow rates.

All materials the barrier, tubing, surface coatings, lubricants, and gaskets need to be able to contain, but not react with, the highly reactive and corrosive UF 6. Because of their kinetic energy at temperatures above absolute zero, all particles undergo diffusion.

Diffusion refers to the process of particles moving from an area of high concentration to one of low concentration. The rate of this movement is a function of temperature, viscosity of the medium, and the size mass of the particles.

Diffusion results in the gradual mixing of materials, and eventually, it forms a homogeneous mixture. Not only do gaseous particles move with high kinetic energy, but their small size enables them to move through small openings as well; this process is known as effusion.

The opening of the hole must be smaller than the mean free path because otherwise, the gas could move back and forth through the hole.