The purification of hydrogen gas is possible by diffusion through a thin palladium sheet. Calculate the number of kilograms of hydrogen that pass per hour (in kg/h) through a 3.1-mm thick sheet of palladium having an area of 0.25 m² at 500C. Assume a diffusion coefficient of 6.0 x 10^-8 m²/s, that the concentrations at the high- and low-pressure sides of the plate are 3.5 and 0.81 kg/m³ (kilogram of hydrogen per cubic meter of palladium), and that steady-state conditions have been attained.

Answer: ______ kg/h