Mass Transfer - Engineering

Q1:

Molecular diffusivity of a liquid

A increases with temperature.

B decreases with temperature.

C may increase or decrease with temperature.

D is independent of temperature.

ANS:A - increases with temperature.

The molecular diffusivity of a liquid generally increases with temperature. Explanation:

  • Molecular diffusivity refers to the ability of molecules to move and spread within a substance due to random motion.
  • Diffusion is a temperature-dependent process. As temperature increases, the kinetic energy of molecules also increases.
  • Higher kinetic energy leads to increased molecular movement and collision frequency, facilitating faster diffusion.
  • Therefore, at higher temperatures, molecules in a liquid have greater thermal energy, allowing them to diffuse more rapidly through the liquid.
  • Conversely, at lower temperatures, molecular motion and diffusion rates are slower due to reduced kinetic energy.
  • Overall, molecular diffusivity tends to increase with temperature for most liquids, although there may be exceptions depending on the specific properties of the liquid and its molecular interactions.
In summary, the molecular diffusivity of a liquid generally increases with temperature due to the higher kinetic energy of molecules, which enhances their ability to move and spread within the liquid.