The rate of diffusion of molecules between two media will be higher if_________?

Step 1: Analyze the question The question asks which condition makes the rate of diffusion between two media higher.

Step 2: Explain the concept Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. The difference in concentration between the two regions is called the concentration gradient.

The rate of diffusion depends on:

• Concentration gradient: a steeper gradient gives a faster rate.
• Temperature: higher temperature gives molecules more kinetic energy, so diffusion is faster.
• Surface area: a larger area gives a faster rate.
• Distance: a shorter distance gives a faster rate.
• Size of molecules: smaller molecules diffuse faster.

Step 3: Evaluate the options

• A. Low concentration difference: the gradient is shallow, so diffusion is slow. ❌
• B. Negligible difference: there is almost no net movement. ❌
• C. High concentration difference: the gradient is steep, so many more molecules move down it, and diffusion is fast. ✅
• D. No difference: this is dynamic equilibrium, with no net diffusion. ❌

Step 4: Answer The rate of diffusion is higher when the difference in concentration between the two media is high.

Tip: Think of a ball rolling down a hill. The steeper the hill (the bigger the concentration gradient), the faster the ball rolls. In WASSCE, whenever you see "rate of diffusion" with "concentration difference," a bigger difference means a faster rate.