ANS:C - increase 'S' and decrease 'G'.

To increase the absorption factor, where G represents the gas flow rate and S represents the solvent flow rate, you should increase 'S' and decrease 'G'. Explanation:

1. Absorption Factor:
   • The absorption factor represents the efficiency of the absorption process, indicating the extent to which the solute (gas) is absorbed by the solvent.
   • It is influenced by various factors, including the flow rates of the gas and solvent, their contact time, the solubility of the solute in the solvent, and the surface area available for contact.
2. Gas and Solvent Flow Rates:
   • In absorption processes, increasing the flow rate of the solvent (S) enhances the contact between the gas and solvent phases, allowing for more efficient absorption of the solute.
   • Conversely, decreasing the flow rate of the gas (G) reduces the dilution of the solute in the gas phase, increasing its concentration gradient and facilitating absorption.
   • Therefore, increasing the flow rate of the solvent (S) and decreasing the flow rate of the gas (G) simultaneously can enhance the absorption factor.
3. Effect of Increasing G and S:
   • Increasing both the gas flow rate (G) and the solvent flow rate (S) simultaneously may not necessarily improve the absorption factor.
   • While increasing the gas flow rate (G) can enhance mass transfer by increasing the contact between the gas and solvent phases, increasing the solvent flow rate (S) can further enhance mass transfer by providing more solvent for absorption.
   • However, there is an optimal balance between the gas and solvent flow rates that maximizes the absorption efficiency, and exceeding this balance may lead to diminishing returns or operational inefficiencies.

In summary, to increase the absorption factor, it is generally more effective to increase 'S' (solvent flow rate) and decrease 'G' (gas flow rate), as this enhances contact between the gas and solvent phases and facilitates efficient absorption of the solute.