The diffusion coefficient D of a gas can be calculated using the Chapman-Enskog equation:D = 3.0 10^-7 T^3/2 / P d1 + d2 M1^1/3 + M2^1/3 ^2 where:- D is the diffusion coefficient in m/s - T is the temperature in Kelvin K - P is the pressure in atm- d1 and d2 are the molecular diameters of the two gases in - M1 and M2 are the molar masses of the two gases in g/mol For oxygen gas O2 in air, we can assume that air is primarily composed of nitrogen gas N2 . The values for the molecular diameters and molar masses are:- d1 O2 = 3.46 - d2 N2 = 3.64 - M1 O2 = 32 g/mol- M2 N2 = 28 g/molAt 25C and atmospheric pressure, the temperature and pressure values are:- T = 25C + 273.15 = 298.15 K- P = 1 atmNow, we can plug these values into the Chapman-Enskog equation:D = 3.0 10^-7 298.15 ^3/2 / 1 3.46 + 3.64 32^1/3 + 28^1/3 ^2 D 2.12 10^-5 m/sSo, the diffusion coefficient of oxygen gas in air at 25C and atmospheric pressure is approximately 2.12 10^-5 m/s.