$.$ A counter$-$current wet scrubbing tower used to remove ammonia from a gas

stream by absorption is operated at a total constant pressure of $2$ atm. Pure water

is supplied to the top of the scrubbing tower. The gas stream, containing $27$ mol$\%$

ammonia vapour and $73$ mol$\%$ air on a dry basis, is fed to the bottom of the tower.

The scrubbed gas containing $0\mathrm{.}5$ mol$\%$ ammonia on dry basis exits the top of the

tower and an aqueous solution of ammonia exits the bottom of the tower $($see

Figure $2\mathrm{.}1).$ The gas stream leaves at $22\mathrm{.}3\backslash$deg C$,$ being saturated with water vapour.

If the ammonia$/$air gas mixture enters the scrubbing tower at $1166$ mol min$1$ on

a dry basis:

i$.$ Calculate the percentage removal of ammonia.