Question

When the concentration of molecules on both sides of a membrane is the same, the molecules will
a.
move across the membrane to the outside of the cell.
b.
stop moving across the membrane.
c.
move across the membrane in both directions.
d.
move across the membrane to the inside of the cell.

Answer 1

C. Move across the membrane in both directions.

However, this answer is a little bit incomplete. Here's why:
It should say: Move across the membrane in both directions at equal rates. Because the concentrations on both sides of the membrane are at equilibrium, no concentration gradient exists and the movement of particles across the membrane is at equilibrium too.
(Answer B is false because the solute particles don't stop moving all of a sudden when the concentrations on both side of the membrane are equal, thus particles will still pass the membrane.)

Hope this helps you understand the principle of diffusion :)

Answer 2

thanks!!!!! :)

Answer 3

Anytime :)