difference between effusion and diffusion

Asked by pulkit2512 | 11th Apr, 2008, 07:25: PM

Expert Answer:

  1. In physics, chemistry and biology, diffusion denotes the mixing of two or more substances or the net motion of a substance from an area of high concentration to an area of low concentration. The theory is that both of these result from the random motion of micro-scale individual agents (such as molecules) giving rise to net changes on the macro-scale. While originally formulated within the framework of the physical sciences, the concept of diffusion has been applied to phenomena such as the manner in which information is spread amongst a population. The chemistry definition of diffusion is the movement of a fluid from an area of higher concentration to an area of lower concentration.
  2. In chemistry, effusion is the process where individual molecules flow through a hole without collisions between molecules. This occurs if the diameter of the hole is considerably smaller than the mean free path of the molecules[1]. According to Graham's law, the rate at which gases effuse is dependent on their molecular weight; gases with a lower molecular weight effuse more quickly than gases with a higher molecular weight. For two gases at the same temperature (and having the same specific heat), and thus having the same kinetic energy, the average molecular speed of each gas can be found using the equation E = (1 / 2)mv2. Thus, lighter molecules have a higher speed. This results in more molecules passing through the hole per unit time. This is why a balloon filled with low molecular weight hydrogen left alone for a reasonable amount of time deflates faster than a separate balloon full of higher molecular weight oxygen.

Answered by  | 11th Jun, 2008, 04:19: AM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.