ANS:B -

In a vapor-liquid contacting equipment, such as a packed column or tray column used in distillation, the overall gas phase mass transfer coefficient (𝐾𝐺KG​) is related to the individual mass transfer coefficients for gas phase (𝐾𝐺KG​) and liquid phase (𝐾𝐿KL​) by the following equation: 1𝐾𝐺=1𝐾𝐿+1𝐾𝐺′KG​1​=KL​1​+KG′​1​ Where:

• 𝐾𝐺KG​ is the overall gas phase mass transfer coefficient.
• 𝐾𝐿KL​ is the liquid phase mass transfer coefficient.
• 𝐾𝐺′KG′​ is a correction factor for gas phase resistance.

This equation is known as the Hatta number equation or the two-film theory equation. It represents the overall resistance to mass transfer in the gas phase as the sum of the resistances in the liquid phase and an additional resistance due to the gas phase itself. The term 𝐾𝐺′KG′​ is introduced to account for any additional resistance to mass transfer in the gas phase, such as resistance due to gas film thickness, gas-phase diffusion, or other factors. It is often assumed to be negligible compared to the liquid phase resistance (𝐾𝐿KL​) in many practical cases. Therefore, the overall gas phase mass transfer coefficient (𝐾𝐺KG​) is inversely related to the sum of the inverse of the liquid phase mass transfer coefficient (𝐾𝐿KL​) and the inverse of the correction factor for gas phase resistance (𝐾𝐺′KG′​).