Diffusivity of Gasses -- Average Collision Diameter & Integral

In summary, the Average Collision Diameter and Integral values used in the diffusion equation are calculated using the kinetic theory of gases and can vary depending on experimental conditions.
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The values for the Average Collision Diameter and Integral are calculated using the kinetic theory of gases, which takes into account the temperature, pressure, and molecular properties of the gas. Specifically, the average collision diameter is calculated from a combination of the root-mean-square velocity (related to temperature) and the mean free path (related to pressure). The integral is calculated by integrating the Boltzmann equation for the mean square displacement of molecules over time. The calculations can be quite complex and the exact values for any given gas-pair diffusivity will vary depending on the conditions of the experiment. The book referenced in the Wikipedia article is a compendium of tabulated values, based on experiments conducted at a variety of temperatures and pressures.
 

1. What is the diffusivity of gases?

The diffusivity of gases refers to the rate at which gases spread or disperse in a given space. It is a measure of how quickly gas molecules move and collide with each other.

2. How is the average collision diameter of a gas determined?

The average collision diameter of a gas is determined by measuring the distance between the centers of two gas molecules during a collision. This value is then averaged over multiple collisions to get a more accurate representation of the gas's average collision diameter.

3. What is the significance of the average collision diameter in determining diffusivity?

The average collision diameter is a crucial factor in determining the diffusivity of gases. It is used in conjunction with the viscosity and temperature of the gas to calculate the gas's diffusivity. A higher average collision diameter means that the gas molecules are larger and will collide less frequently, resulting in a lower diffusivity.

4. How does the integral of the collision diameter affect gas diffusivity?

The integral of the collision diameter is used to calculate the average distance between gas molecules during collisions. This value, along with the average collision diameter, is used in the equation for diffusivity. A larger integral value means that the gas molecules are more closely packed and will collide more frequently, resulting in a higher diffusivity.

5. Are there any factors that can affect the diffusivity of gases?

Yes, there are several factors that can affect the diffusivity of gases. These include temperature, pressure, and the type of gas. Generally, as temperature increases, the diffusivity of gases also increases. Higher pressures can also decrease diffusivity due to increased molecular interactions. Different gases also have different diffusivity values due to variations in their molecular structures and sizes.

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