It is desired to calculate the rate of diffusion of CO2 gas in air at steady state through a loosely packed bed of sand at 276 K and a total pressure of 1.013 × 10 5 Pa. The bed depth is 1.25 m and the void fraction ε is 0.30. The partial pressure of CO2 is 2.026 × 10 3 Pa at the top of the bed and 0 Pa at the bottom. Use a τ of 1.87.

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.