$5\mathrm{.}4$ The equilibrium adsorption of benzene vapor on a certain activated charcoal at $33\mathrm{.}3C$ is

reported as follows:

$($a$)$ A nitrogen$-$benzene vapor mixture containing $1\mathrm{.}0\%$ benzene by volume is to be passed

countercurrently at the rate $100f\frac{t^3}{m}in(4\mathrm{.}72{10}^{-2}\frac{m^3}{s})$ to a moving stream of the activated

charcoal so as to remove $95\%$ of the benzene from the gas in a continuous process. The entering

charcoal contains $15c{m}^3$ benzene vapor $($at STP$)$ adsorbed per gram charcoal. The temperature and

total pressure are to be maintained at $33\mathrm{.}3C$ and $1$stdatm, respectively, throughout. Nitrogen is not

adsorbed. What is the least amount of charcoal which can be used per unit time? If twice as much is

used, what will be the concentration of benzene adsorbed upon the charcoal leaving?

$($b$)$ Repeat part $($a$)$ for a cocurrent flow of gas and charcoal.

$($c$)$ Charcoal which has adsorbed upon it $100c{m}^3($at STP$)$ tenzene vapor per gram is to be

stripped at the rate $100l\frac{b}{h}(45\mathrm{.}4k\frac{g}{h})$ of its benzene content to a concentration of $55c{m}^3$

adsorbed benzene per gram charcoal by continuous countercurrent contact with a stream of pure

nitrogen gas at $1$ std atm. The temperature will be maintained at $33\mathrm{.}3C.$ What is the minimum rate

of nitrogen flow? What will be the benzene content of the exit gas if twice as much nitrogen is fed?

What will be the number of stages? Ans.: $3$ theoretical stages.