To calculate the diffusivity of oxygen gas in air at 25C and 1 atm pressure, we can use the Chapman-Enskog equation, which is given by:D = 3/16 * k * T / * d^2 * P where:D is the diffusivity m/s k is the Boltzmann constant 1.38064852 10 J/K T is the temperature in Kelvin K d is the collision diameter m P is the pressure Pa First, we need to convert the temperature from Celsius to Kelvin:T = 25C + 273.15 = 298.15 KNext, we need to find the collision diameter d for oxygen gas. The collision diameter of oxygen is approximately 3.46 10 m.Now, we need to convert the pressure from atm to Pa:1 atm = 101325 PaNow, we can plug these values into the Chapman-Enskog equation:D = 3/16 * 1.38064852 10 J/K * 298.15 K / * 3.46 10 m * 101325 Pa D 2.12 10 m/sSo, the diffusivity of oxygen gas in air at 25C and 1 atm pressure is approximately 2.12 10 m/s.