ANS:C - increases

In a randomly packed counter-current gas-liquid absorption column, with an increase in the liquid flow rate at a fixed gas velocity, the gas pressure drop typically increases. Here's why:

1. Liquid Flow Rate Increase: Increasing the liquid flow rate in a counter-current absorption column enhances the mass transfer efficiency by providing more contact between the gas and liquid phases. This increased contact allows for better absorption of the solute from the gas phase into the liquid phase.
2. Effect on Gas Pressure Drop: The pressure drop in a packed column is primarily influenced by the resistance offered by the packing material to the flow of gas. When the liquid flow rate increases, more liquid flows downward through the packed bed, creating additional resistance for the upward flow of gas. As a result, the gas velocity through the packed bed decreases, leading to an increase in gas pressure drop.
3. Relationship to Gas Velocity: The gas pressure drop is directly related to the gas velocity. As the gas velocity decreases due to increased liquid flow rate, the gas pressure drop increases, as the gas must overcome greater resistance from the liquid phase.