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 through a 7.8-mm-thick sheet of palladium having an area of 0.80 m^2 at 500°C. Assume a diffusion coefficient of 6.7 x 10^-8 m^2/s, that the concentrations at the high- and low-pressure sides of the plates are 2.8 and 0.72 kg/m^3 of hydrogen per cubic meter of palladium, and that steady-state conditions have been attained.