The rate of diffusion across an exchange surface is proportional to . Surface area is doubled and the thickness is halved, with unchanged. By what factor does the rate change?
Answer and explanation
Correct answer: B. It increases by a factor of
- Step 1: Doubling doubles the rate.
- Step 2: Halving doubles the rate again.
- Step 3: The combined factor is .
Answer
It increases by a factor of .
Why not the others: It increases by a factor of : accounts for only one of the two changes. It stays the same: the two changes act in the same direction, not in opposite directions. It increases by a factor of : squares one of the changes.
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