$9.$ The absorption factor $($AF$)$ is a key parameter that influences the solvent $\_\_\_\_\_\_$ strategy, the efficiency of $\_\_\_\_$ removal from the gas phase, and the design of the $\_\_\_\_\_\_$ system.

$10.$ The height of a transfer unit $($HTU$)$ is significant in calculating the total $\_\_\_\_\_\_$ height needed for achieving the desired separation, which depends on the $\_\_\_\_$ of the packing material and the solvent $\_\_\_\_\_\_$ rate.

$11.$ When selecting a solvent for an absorption process, its $\_\_\_\_\_\_,\_\_\_\_$ capacity, and effect on the $\_\_\_\_\_\_$ of transfer units $($NTU$)$ must be considered.

$12.$ The graphical method for stage estimation in absorption columns relies on plotting the equilibrium $\_\_\_\_\_\_$ against the operating $\_\_\_\_,$ which helps in visually determining the number of $\_\_\_\_\_\_$ stages required.