At constant pressure, the mean free path 1l2 of a gas molecule is directly proportional to temperature. At constant temperature, l is inversely proportional to pressure. If you compare two different gas molecules at the same temperature and pressure, l is inversely proportional to the square of the diameter of the gas molecules. Put these facts together to create a formula for the mean free path of a gas molecule with a proportionality constant (call it Rmfp, like the ideal-gas constant) and define units for Rmfp.

Verified step by step guidance

1. Step 1: From the problem, we know that the mean free path (l) of a gas molecule is directly proportional to temperature (T) at constant pressure. This can be written as l ∝ T.
2. Step 2: We also know that at constant temperature, l is inversely proportional to pressure (P). This can be written as l ∝ 1/P.
3. Step 3: Furthermore, if we compare two different gas molecules at the same temperature and pressure, l is inversely proportional to the square of the diameter (d) of the gas molecules. This can be written as l ∝ 1/d².
4. Step 4: Combining these three relationships, we can write a formula for the mean free path as l = Rmfp * (T/P) * (1/d²), where Rmfp is the proportionality constant, similar to the ideal-gas constant.
5. Step 5: The units for Rmfp can be derived from the equation. Since l, T, P, and d have units of length, temperature, pressure, and length respectively, the units for Rmfp would be (length² * pressure) / (temperature * length²) = pressure/temperature. This is the same as the ideal gas constant R, which has units of J/(mol*K) in SI units, or L*atm/(mol*K) in common chemistry units.

Key Concepts

Mean Free Path

The mean free path is the average distance a gas molecule travels between collisions with other molecules. It is influenced by factors such as temperature, pressure, and the size of the molecules. A longer mean free path indicates fewer collisions, while a shorter mean free path suggests more frequent interactions among gas particles.

Gas Laws

Gas laws describe the behavior of gases in relation to pressure, volume, and temperature. Key laws include Boyle's Law, which states that pressure is inversely proportional to volume at constant temperature, and Charles's Law, which states that volume is directly proportional to temperature at constant pressure. Understanding these relationships is crucial for deriving formulas related to gas behavior.

Proportionality and Constants

In physics and chemistry, proportionality indicates how one quantity changes in relation to another. When deriving formulas, constants like Rmfp serve as proportionality constants that relate different variables. For the mean free path, the constant Rmfp would encapsulate the effects of temperature, pressure, and molecular size, allowing for a unified equation to predict gas behavior.