Answer: Option (A) is the correct answer.
Explanation:
Rate of diffusion is defined as the total movement of molecules from a region of higher concentration to lower concentration.
The interaction between medium and the material is responsible for the rate of diffusion of a material or substance.
A small concentration gradient means small difference in the number of molecules taking part in a reaction. So, when there no large difference between the concentration then there won't be much difference in the rate of diffusion of a material.
Whereas a higher concentration of molecules will lead to more number of collisions due to which frequency of molecules increases. Therefore, rate of diffusion will also increase.
Small molecule size will also lead to increases in rate of diffusion. This is because according to Graham's law rate of diffusion is inversely proportional to molar mass of an element. Hence, smaller size molecule will have smaller mass. As a result, rate of diffusion will be more.
High temperature means more kinetic energy of molecules due to which more number of collisions will be there. Hence, rate of diffusion will also increase.
Thus, we can conclude that out of the given options a small concentration gradient is least likely to increase the rate of diffusion.
