In a surface treatment process metallic sheets coated with a metal oxide layer are reduced in a

hydrogen atmosphere at $400C$ at $1$ bar pressure.

MeO$+H_{2}Me+H_{2}O$

In this process hydrogen gas migrates to the surface through a thin diffusion film where is it

consumed rapidly $-$ hence you can assume its concentration at the surface is $0.$ Likewise

water vapour formed at the surface migrates back into the bulk hydrogen stream, where its

concentration is negligibly small. Given the diffusivity of water vapour through hydrogen at

$400C$ is ${10}^{-5}\frac{m^2}{s},$ determine the thickness of the diffusion layer, if the surface is reduced to

metal to a depth of $10m$ in $2$ seconds. Provide diagram for illustration.

${}_{\text{M}\text{e}\text{O}}=2\mathrm{.}8\frac{g}{c}{m}^3,M_{\text{M}\text{e}\text{O}}=80\frac{g}{m}ol$