Factors Affecting the Rate of Diffusion Flashcards

All 7 cards in this deck

Name the three factors that affect the rate of diffusion.

Surface area, concentration gradient (concentration difference) and diffusion distance (membrane thickness).

State Fick's law as a formula.

rate of diffusion $\propto \dfrac{\text{surface area} \times \text{concentration difference}}{\text{thickness of membrane}}$

What are the steps to calculate a relative rate of diffusion using Fick's law?

e.g. surface area $= 4$, concentration difference $= 6$, membrane thickness $= 2$

1. Multiply surface area by concentration difference: $4 \times 6 = 24$
2. Divide by the membrane thickness: $24 \div 2 = 12$
3. Relative rate of diffusion $= 12$ (no units)

True or false? Doubling the thickness of an exchange surface doubles the rate of diffusion.

False. Rate is inversely proportional to thickness, so doubling the thickness halves the rate.

Using Fick's law, what happens to the rate of diffusion if the surface area is doubled and everything else stays the same?

The rate of diffusion doubles — rate is directly proportional to surface area.

True or false? The steeper the concentration gradient, the faster the rate of diffusion.

True. Rate of diffusion is proportional to the concentration difference across the surface.

True or false? In an agar cube experiment, dye reaches the centre of the largest cube in the shortest time.

False. The smallest cube is coloured throughout first — it has the largest surface area : volume ratio and the shortest diffusion distance to its centre.