Does diffusion coefficient depend on molecular weight?
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Does diffusion coefficient depend on molecular weight?
Diffusion in Liquids Consequently, diffusion coefficients in liquids are directly proportional to the temperature of the fluid but do not depend on the molecular weight of the substance diffusing.
How do you find the molecular weight from the diffusion coefficient?
D = kT/6 π μ rh (Stokes-Einstein) For a molecular mass 64.5 kDa for a globular protein we expect a particle radius around 3.5 nm . Using 273K and SI units: Thus, D = 1.38E-23*273/[6π*10E-6*(3.5E-9)]
What is molecular and turbulent diffusion?
Turbulent diffusion is the dominant transfer process in the free atmosphere, although molecular diffusion continues to operate and is responsible for the ultimate degradation of turbulent energy into heat.
Does molecular size affect diffusion?
We know that higher the molecular mass bigger is the size of the molecule. The expression for the Graham’s law of diffusion shows that the rate of diffusion is inversely proportional to the molecular mass i.e. the rate of diffusion is inversely proportional to the size of the molecule.
Does a higher molecular weight diffuse faster?
Similar to effusion, gases with lower molecular weights (which have a higher rms speed) diffuse faster than gases with higher molecular weights.
What is diffusion coefficient in liquid?
The diffusion coefficient is a function of the fluid, size of the diffusing molecule (larger molecules diffuse more slowly), temperature, obstruction of diffusion by pore structure in sediments or other materials, and the rate of mixing of water.
What is the relationship between molecular radius and diffusion coefficient?
According to the Stokes–Einstein equation, the diffusion coefficient of a molecule is expected to increase in inverse proportion to its approximate radius. Therefore, a larger molecular weight is related to a larger approximate radius, so that the diffusion coefficient is generally smaller.
How do you calculate molecular diffusion?
Diffusion coefficient is the proportionality factor D in Fick’s law (see Diffusion) by which the mass of a substance dM diffusing in time dt through the surface dF normal to the diffusion direction is proportional to the concentration gradient grad c of this substance: dM = −D grad c dF dt.
What is the molecular description of diffusion?
Diffusion is defined as the movement of individual molecules of a substance through a semipermeable barrier from an area of higher concentration to an area of lower concentration [34].
Do smaller molecules diffuse faster?
This laboratory shows that diffusion of molecules occurs in gels. It also shows that molecules diffuse faster at higher temperature and small molecules diffuse faster than larger ones.
What is the relationship between rate of diffusion and molecular weight?
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.
How does molecular size affect diffusion rate?
How does molecular mass affect the rate of diffusion?
Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly.
