Mass transfer coefficient in counter$-$diffusion. The gas phase reaction $AB$ occurs on the surface of a catalyst in the form of a wire gauge. The bulk concentration of the species A is $0\mathrm{.}002$kmo$\frac{l}{m^3}$ and the rate of reaction of $A$ is measured at $0\mathrm{.}08$kmol per hour per $m^2$ area of the catalyst. If the reaction is instantaneous and the entire diffusional resistance to the transport of the reactive species from the bulk gas to the catalyst surface is offered by a stagnant film of gas, calculate $($a$)$ the thickness of the film, $($b$)$ the mass transfer coefficients $k^{\text{'}}G,k^{\text{'}}y$ and $($c$)$ the concentration of A halfway the gas film. Given: total pressure $=\frac{1\mathrm{.}5}{b}ar,$ temperature $=250C,D_{AB}=0\mathrm{.}16c\frac{m^2}{s}$ at $\frac{1}{b}ar$ and $100C.$