kinetics theory of gases

Postulates of kinetics theory :-

 

     Suppose a container with volume v contain a very large numbers N of identical molecules,each with mass m. Then, the kinetics theory postulates the following-

(1) The molecules behave a point particles that are small compared to the size of the container and to the average distance between molecules.

(2) The molecules are in constant motion. Each molecules collides occasionally with a wall of the container. These collisions are perfectly elastic.

(3) There is no force of attraction among the gas molecules and between the gas molecules and walls of the container.

(4) The container walls are right and infinitely massive and do not move.

(5) The molecules obey Newton's law of motion.

(6) The time of collision is much less than the averaged time between two successive collision.

Meaning of elastic collisions:-

If a molecule with velocity u strikes a wall align along y-axis, then the collision is elastic if

• velocity component parallel to wall y-component does not change, i.e., 

• velocity Component perpendicular to wall (x-component ) reverse direction, i.e., 

• Speed v does not change, i.e., 

Note: 

           We will follow these notation through out the book.

N= Number of molecules in the gas

n= number of moles in the gas

N A = avagadro number

 Where,

            
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