Graham’s law of diffusion

Graham s law of diffusion This law states that the rates at which two gases diffuse are inversely proportional to their densities, i.e. 

Graham s Law of Diffusion. The rates at which gases diffuse under the same conditions of temperature and pressure are inverseiy proportionai to the square roots of their densities ... 

This result was first observed experimentally by Graham and is called Graham s law of diffusion. Knudsen diffusion membranes have been used to separate gas isotopes that are difficult to separate by other methods, for example tritium from... 

From 1943 to 1945, Graham s law of diffusion was exploited for the first time, to separate U235F6 from U238F6 as part of the Manhattan project. Finely microporous metal membranes were used. The separation plant, constructed in Knoxville, Tennessee, represented the first large-scale use of gas separation membranes and remained the world s largest membrane separation plant for the next 40 years. However, this application was unique and so secret that it had essentially no impact on the long-term development of gas separation. 

A less widely used approach (8,9) has been to expose a surface of pesticide to an air flow under conditions of a rapid rate of air change such that the concentration of the pesticide in the air surrounding the stagnant boundary layer is far below saturation. Under these conditions the relative rates of diffusion of two pesticides will be inversely related to the square root of their respective molecular weights (Graham s law of Diffusion) and directly related to their saturated vapour concentrations in the boundary layer. 

Effusion is the passage of a gas through a tiny hole usually into a chamber of lower pressure. Thomas Graham experimentally determined that the rate of effusion is inversely proportional to the square root of the molecular mass. Graham s law of diffusion states ... 

It was the Scottish chemist, Thomas Graham, whose research pertaining to the diffusion of gases and liquids, not only led to Graham s law of diffusion, but also provided some of the first clues to the existence of large molecules. 

Describe the relationships between gas behavior and chemical formulas, such as those expressed by Graham s law of diffusion, Gay-Lussac s law of combining volumes, and Dalton s law of partial pressures. 

Solving this equation for the ratio of speeds between Va and Vb gives Graham s law of diffusion. 

This problem can be solved using Graham s law of diffusion, which compares molecular speeds. ... 

Skill 3.1f-Solve problems using Dalton s law of partial pressures and Graham s Laws of diffusion... 

Graham s law (of diffusion) The principle that gases diffuse at a rate that is inversely proportional to the square root of their density. Light molecules diffuse faster than heavy molecules. The principle is used in the separation of isotopes. The law is named for the Scottish chemist Thomas Graham (1805-69). 

In 1907, J. J. Thomson observed that when a vacuum tube is filled with neon gas under low pressure, the introduction of magnetic and electric fields produces two parabolic luminescent paths of canal rays (see chapter 1), corresponding to two different masses (20 and 22) for charged particles. The potentially revolutionary results were treated cautiously since impurities could be the cause. In 1909, Francis William Aston (1877-1945) became Thomson s assistant at Cambridge. Aston and Thomson attempted to apply Graham s law of diffusion to separate the two different components of neon gas and, after thousands of cycles of diffusion operations, obtained in 1913 a mass difference of 0.7 between the hghter and heavier fractions. World War I delayed continuation of this groundbreaking project for a few years. 

If the system is open, the flux of the component 2 is related to that of the component 1 by the Graham s law of diffusion (eq. 7.7-7), hence the above equation can be rewritten to yield an expression for the diffusion flux of the component 1 ... 

Knowing the flux of the component 1, the flux of the component 2 is calculated from the Graham s law of diffusion. 

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