$($GATE $2002)$ A counter current multistage stripper as shown in figure below

is used to remove an impurity from a cream using pure steam. $100k\frac{g}{h}r$ of

liquid cream containing $20$ parts per millions $($ppm$)$ by weight of impurity is

fed to the stripper. It is desired to reduce the concentration of impurity in

the cream to $1ppm.$ Assume that the liquid cream does not evaporate and

steam does not condense. The equilibrium relation is $y=10x,$ where $y$ and $x$

are the ppm of impurity in steam and cream, respectively.

a$)$ Indicate schematically on a $x-y$ plot, the equilibrium line and operating line

for minimum steam flow rate.

b$)$ Determine the minimum flow rate of steam required.

c$)$ If the rate of steam input to the stripper is $1\mathrm{.}5$ times the minimum,

determine the required integral number of theoretical stages.A counter current plate absorber is to be installed for scrubbing

of an air mixture containing $5\%$ ammonia by volume. The scrubber is fed

with water containing $0\mathrm{.}002$ mole NH$3$ per mole of water. The scrubbing

water flows at a rate of $1\mathrm{.}0$ mole water per mole air. It is necessary to absorb

$85$ percent of the ammonia present in the gas by operating the absorber at

$200$C$.$