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Kinetic Theory of Gases

The kinetic theory of gases can be explored in terms of the following assumptions. The theory tries to answer the questions regarding the various properties of gases. It also gives the relationship between the kinetic energy of the molecules and the absolute temperature. The important points in kinetic theory of gases are listed below:
  1. A gas consists of small particles (sizes are considered relatively negligible) known as molecules, which are separated widely apart and thus the gas container is mostly empty.
  2. The molecules are in a state of continuous random motion, and colliding against each other and also against the sides of the container, and furthermore the collisions are elastic.
  3. These collisions result in the pressure of the gas.
  4. The molecules are expected to travel in straight lines at different speeds in all directions.
  5. The forces (attractive or repulsive) between the molecules are negligible.
  6. The average kinetic energy of the molecules is proportional to the temperature. 

Ideal gas molecules travel randomly in straight lines at different speeds.

Some Aspects Related to Kinetic Theory

The main aspect of kinetic theory is that the molecules in a gas are in a state of continuous random motion. The speed of molecules depends on the temperature, and can have a range of values. Maxwell's distribution curve is perfect to analyze this fact. In the Maxwell's distribution curve, the relative number of molecules are plotted against the molecular speed on the x-axis. Take a look at the curve in.
Note that the speed corresponding to the maximum number of molecules is called the most probable speed. This is always smaller than the average speed, which is in turn smaller than the root-mean-square speed (rms speed).
The formula for root-mean-square speed is given below:


Here, R is the gas constant, T is the absolute temperature, and M is the molar mass of the gas.

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