The figure below illustrates protons (the circles) separated by a membrane permeable to the protons and water. What will happen to the protons as time passes and the system equilibrates?
A) The protons will neutralize.
B) All of the protons will move from compartment I to compartment II.
C) All of the protons will move from compartment II to compartment I.
D) The concentration of the protons in compartments I and II will become equal.
E) Nothing will happen.

Question

The figure below illustrates protons (the circles) separated by a membrane permeable to the protons and water. What will happen to the protons as time passes and the system equilibrates? 
A) The protons will neutralize. 
B) All of the protons will move from compartment I to compartment II. 
C) All of the protons will move from compartment II to compartment I. 
D) The concentration of the protons in compartments I and II will become equal. 
E) Nothing will happen.

Quizplus · Accepted Answer

Since the membrane is permeable to both water and protons, both of them will diffuse in order to achieve equilibrium. However, protons are charged particles and will create an electrochemical gradient across the membrane. As more protons accumulate on one side of the membrane, the difference in electrochemical potential will increase. This will result in more protons moving back across the membrane towards the side with fewer protons until the concentration becomes equal on both sides (equilibrium). Therefore, the concentration of protons in compartments I and II will become equal over time.

The Figure Below Illustrates Protons (The Circles) Separated by a Membrane