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  2. Molecular diffusion - Wikipedia

    en.wikipedia.org/wiki/Molecular_diffusion

    The rate of diffusion N A is usually expressed as the number of moles diffusing across unit area in unit time. As with the basic equation of heat transfer, this indicates that the rate of force is directly proportional to the driving force, which is the concentration gradient.

  3. Mass diffusivity - Wikipedia

    en.wikipedia.org/wiki/Mass_diffusivity

    Typically, a compound's diffusion coefficient is ~10,000× as great in air as in water. Carbon dioxide in air has a diffusion coefficient of 16 mm 2 /s, and in water its diffusion coefficient is 0.0016 mm 2 /s. [1] [2] Diffusivity has dimensions of length 2 / time, or m 2 /s in SI units and cm 2 /s in CGS units.

  4. Fick's laws of diffusion - Wikipedia

    en.wikipedia.org/wiki/Fick's_laws_of_diffusion

    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 ...

  5. Diffusion - Wikipedia

    en.wikipedia.org/wiki/Diffusion

    The diffusion coefficient is the coefficient in the Fick's first law = /, where J is the diffusion flux (amount of substance) per unit area per unit time, n (for ideal mixtures) is the concentration, x is the position [length].

  6. Graham's law - Wikipedia

    en.wikipedia.org/wiki/Graham's_law

    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.

  7. Diffusivity - Wikipedia

    en.wikipedia.org/wiki/Diffusivity

    Diffusivity is a rate of diffusion, a measure of the rate at which particles or heat or fluids can spread. It is measured differently for different mediums. Diffusivity may refer to: Thermal diffusivity, diffusivity of heat; Diffusivity of mass: Mass diffusivity, molecular diffusivity (often called "diffusion coefficient")

  8. Mass transfer coefficient - Wikipedia

    en.wikipedia.org/wiki/Mass_transfer_coefficient

    In engineering, the mass transfer coefficient is a diffusion rate constant that relates the mass transfer rate, mass transfer area, and concentration change as driving force: [1] = ˙ Where: is the mass transfer coefficient [mol/(s·m 2)/(mol/m 3)], or m/s

  9. Diffusion-controlled reaction - Wikipedia

    en.wikipedia.org/wiki/Diffusion-controlled_reaction

    Diffusion-controlled (or diffusion-limited) reactions are reactions in which the reaction rate is equal to the rate of transport of the reactants through the reaction medium (usually a solution). [1] The process of chemical reaction can be considered as involving the diffusion of reactants until they encounter each other in the right ...