n unglazed porcelain plate $5$ mm thick has an average

pore diameter of $0\mathrm{.}2\backslash$mu m$.$ Pure oxygen gas at an absolute pressure of $20$

mm Hg$,400$K$,$ on one side of the plate passed through at a rate of $0\mathrm{.}10$

cm$3/$cm$2$s when the pressure on the downstream side was so low as to

be considered negligible. $($a$)$ Determine the Knudsen number for flow

inside the pores. $($b$)$ Estimate the rate of passage of hydrogen gas

through the plate at $300$ K and an absolute pressure of $10$ mm Hg$,$

with negligible downstream pressure