a gas stream containing a mixture of nh$3$ and air at a flow rate of $57\mathrm{.}8$ kg mol$/$h comprises $4\mathrm{.}0$ mol $\%$ nh$3$ in the total gas. the nh$3$ content is decreased to $0\mathrm{.}5$ mol $\%$ in a packed absorption tower at $293$ k and $1\mathrm{.}013$ x $105$ pa$.$ a stream of pure water is introduced to the column at a flow rate of $68\mathrm{.}8$ kg mol$/$h$.$ the tower$$s diameter is $0\mathrm{.}747$ metres. the film mass transfer coefficients are provided as: k$$y a$=0\mathrm{.}0739$ kg mol$/$s m$3.$mol frac k$$x a$=0\mathrm{.}169$ kg mol$/$s$.$m$3$ mol frac.