Question

Diffusion of solid in another's solid is very slow give reason

Answer 1

Your answer :

Diffusion : The spreading out of substances with another substance due to motion of its particles is called diffusion.
The diffusion of one substance into another substance takes place until a uniform mixture is obtained.

The diffusion of solid in another solid is a slow process because particles of solid are fixed they cannot move from their respective place but they show little vibrations. So, because the particles do not move in a solid diffusion becomes slow.

Hope this helps.

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Answer 2

This is because the density is approximately same.