The diffusion coefficient of a gas in air can be calculated using the Chapman-Enskog equation:D = 3.03 10^-7 * T^3/2 / P * M1^1/3 + M2^1/3 ^2 where D is the diffusion coefficient in cm/s , T is the temperature in Kelvin, P is the pressure in atm, M1 and M2 are the molar masses of the two gases in g/mol.For oxygen O2 in air, we can assume air to be primarily composed of nitrogen N2 . The molar masses of O2 and N2 are 32 g/mol and 28 g/mol, respectively. Room temperature is 25C, which is equivalent to 298.15 K, and standard atmospheric pressure is 1 atm.Plugging these values into the equation:D_O2 = 3.03 10^-7 * 298.15^3/2 / 1 * 32^1/3 + 28^1/3 ^2 D_O2 0.211 cm/sFor water vapor H2O in air, the molar mass of H2O is 18 g/mol. Using the same equation:D_H2O = 3.03 10^-7 * 298.15^3/2 / 1 * 18^1/3 + 28^1/3 ^2 D_H2O 0.243 cm/sComparing the two diffusion coefficients, the diffusion coefficient of water vapor in air 0.243 cm/s is slightly higher than that of oxygen in air 0.211 cm/s under the same conditions of room temperature and standard atmospheric pressure. This means that water vapor diffuses slightly faster in air than oxygen.