how does diffusion relate to the molecular weight of substance?

Answer 1

This is a somewhat complex issue. Simplistically, the diffusion coefficient of a substance is inversely proportional to the molecular weight of the substance. Thus the larger the molecular weight, the more slowly it diffuses.

The first study investigating the relationship between diffusion coefficients and molecular weights was performed in 1897, when it was proposed that the diffusion coefficient, D, was inversely proportional to the square root of the molecular weight, M. However, further studies demonstrated that this is not applicable to all molecules because, in the case of unrelated molecules, a change in molecular weight may fail to result in a proportionate change in molecular dimensions. In fact, a relationship between molecular weight and diffusion coefficient is today considered to exist only for homologous compounds. Furthermore while the relationship is still considered to be an inverse proportional one, the power of the inverse proportion may vary.

Answer 2

Graham's law states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight. Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other.

Answer 3

It is the difference in how quickly the molecular substance will diffuse or dissipate. It also depends on what kind of product it is submersed in.

High Molecular weight in low density substance will move slower than a low molecular weight in a low dense substance.The same concept goes for high weight in high dense substance moves much slower than low weight in low substance.
The molecular weight has to do with size of molecule as well as density of molecule which gives it its' weight as well.

Hope this helps

Answer 4

The lower the molecular weight the faster the diffusion.