Question

At room temperature, the free path of molecules present in air is approximately-
1. 10^-7 /m
2. 10^-4 /m
3. 10^-10 /m
4. 10^-13 /m

Answer 1

Correct Answer - Option 2 : 10^-4 /m

Concept:

Mean Free Path (λ): 

• The distance travelled by a gas molecule between two successive collisions is known as a free path.
• During two successive collisions, a molecule of gas moves in a straight line with constant velocity.
• The average distance that a particle can travel between two successive collisions with other particles.

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​\(\lambda = \frac{{Total\;distance\;travelled\;by\;a\;gas\;molecule\;between\;successive\;collisions\;\;}}{{Total\;number\;of\;collisions}}\)

\(\Rightarrow \lambda = \frac{1}{{\sqrt 2 \pi n{d^2}}}\)

Where,

n = number of molecules per unit volume and

d = diameter of a molecule​