Velocities and Effusion

5 Other ideal Gas Properties Mixture Velocities and Effusion 

In a mixture of two or more gases, collisions eventually make the molecules achieve the same temperature, and hence the same kinetic energy. However, this implies that they have different velocities. If the two gases are labeled A and B, Equation 7.19 implies 

Molecular beams are very important tools for characterizing intermolecular and intramolecular reactions. In fact, the 1988 Nobel Prize in Chemistry was awarded to Yuan Lee, Dudley Herschbach, and John Polanyi for studies which were mostly made possible by this technique. A particularly useful variant is the supersonic molecular beam, which in the simplest case pushes a high-pressure mixture of helium and trace amounts of some larger guest molecule through a nozzle. When the helium atoms enter the 

FIGURE 7.6 Gases pour out of a box into an evacuated region at rates proportional to their speeds, hence proportional to 1 / ffm. Thus a mixture of gases with different masses can be separated by this method. 

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