$2\mathrm{.}10$ Ammonia is being cracked on a solid catalyst according to the reaction

$2N{H}_3{N}_2+3H_2$

At one place in the apparatus, where the pressure is $1std$ atm abs and the temperature $200C,$ the

analysis of the bulk gas is $33\mathrm{.}33\%N{H}_3(A),16\mathrm{.}67\%N_2($B$),$ and $50\mathrm{.}00\%H_2($C$)$ by volume. The

circumstances are such that $N{H}_3$ diffuses from the bulk$-$gas stream to the catalyst surface, and the

products of the reaction diffuse back, as if by molecular diffusion through a gas film in laminar flow

$1mm$ thick. Estimate the local rate of cracking, $kgNH$

considered to occur if the reaction is diffusion$-$controlled $($chemical reaction rate very rapid$)$ with the

concentration of $N{H}_3$ at the catalyst surface equal to zero.

Ans.: $0\mathrm{.}0138k\frac{g}{m^2}*s.$