$1.()$ The gas ammonia $($A$)$ is diffusing at steady state through N$2($B$)$ by equimolar counter diffusion in a conduit $0\mathrm{.}5$ m long at $25\backslash$deg C and a total pressure of $101\mathrm{.}32$ kPa abs$.$ The partial pressure of ammonia at the left end is $20\mathrm{.}0$ kPa and at the other end $5\mathrm{.}0$ kPa. The cross section of the conduit is in the shape of a circle, and the diameter being $0\mathrm{.}100$ m at the left and tapering uniformly to $0\mathrm{.}050$ m at the right end. Calculate the molar transfer rate of ammonia in kg mol$/$s$.$ The diffusivity $($DAB$)$ is $0\mathrm{.}230$ x $10-4$ m$2/$s$.$