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Effusion occurs through an orifice smaller than the mean free path of the particles in motion, whereas diffusion occurs through an opening in which multiple particles can flow through simultaneously. In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the ...
Rate 1 is the rate of effusion for the first gas. (volume or number of moles per unit time). Rate 2 is the rate of effusion for the second gas. M 1 is the molar mass of gas 1 M 2 is the molar mass of gas 2. Graham's law states that the rate of diffusion or of effusion of a gas is inversely proportional to the square root of its molecular weight.
Therefore, the "net" movement of oxygen molecules (the difference between the number of molecules either entering or leaving the cell) is into the cell. In other words, there is a net movement of oxygen molecules down the concentration gradient. In astronomy, atomic diffusion is used to model the stellar atmospheres of chemically peculiar stars.
The self-diffusion coefficient of neat water is: 2.299·10 −9 m 2 ·s −1 at 25 °C and 1.261·10 −9 m 2 ·s −1 at 4 °C. [2] Chemical diffusion occurs in a presence of concentration (or chemical potential) gradient and it results in net transport of mass. This is the process described by the diffusion equation.
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
Gaseous diffusion is based on Graham's law, which states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass. For example, in a box with a microporous membrane containing a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules, if the ...
Molecular diffusion occurs in gases, liquids, and solids. Diffusion is a result of thermal motion of molecules. Usually, convection occurs as a result of the diffusion process. The rate at which diffusion occurs depends on the state of the molecules: it occurs at a high rate in gases, a slower rate in liquids, and an even slower rate in solids.
Knudsen diffusion, named after Martin Knudsen, is a means of diffusion that occurs when the scale length of a system is comparable to or smaller than the mean free path of the particles involved. An example of this is in a long pore with a narrow diameter (2–50 nm) because molecules frequently collide with the pore wall. [ 1 ]