For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law.

ANS:A - increases

According to Knudsen's law, the permeability of gases through a capillary tube decreases with an increase in temperature. Explanation:

1. Knudsen's law describes the flow of gases in the molecular flow regime, where the mean free path of gas molecules is comparable to or larger than the diameter of the capillary tube.
2. In this regime, gas molecules move independently, colliding infrequently with each other and the walls of the capillary. Therefore, the flow behavior is significantly influenced by molecular collisions and interactions.
3. As temperature increases, the average kinetic energy of gas molecules also increases. This leads to higher molecular velocities and more frequent collisions with the walls of the capillary.
4. The increased collision frequency results in greater resistance to gas flow through the capillary, reducing the permeability.
5. Conversely, at lower temperatures, gas molecules have lower kinetic energies, resulting in fewer collisions with the capillary walls and higher permeability.
6. Therefore, according to Knudsen's law, the permeability of gases through a capillary decreases with an increase in temperature.