If the diffusion coefficient doubles, and the average diffusion distance across a membrane remains the same, what can be said about the time it takes to cross the membrane g

time taken will be halved

Explanation:

we have

  ..................(1)

where

t = time elapsed since diffusion began

= mean distance traveled by the diffusion solute

D = Diffusion coefficient

now, according to the conditions given in the question

when, diffusion coefficient (D) doubles i.e D' = 2D

Average diffusion distance remains same i.e

substituting the values in the equation we get

or

or

...............(2)

hence, on comparing equation (1) and (2) we can say that the time taken will be halved when the diffusion coefficient doubles and the mean distance traveled remains the same

just took the test its not "d"