Between two membranes, there are solutions of the same substance with different concentrations. According to the law of concentration gradient, a chemical equilibrium will be established between the systems such that the solvent, water, from the less dilute solution will move to the more dilute one, while the substance from the more concentrated solution will tend to move to the less concentrated one (Buckley, 2020).
However, a semipermeable membrane alters the kinetics of such an equilibrium. More specifically, since the membrane is permeable to potassium ions — and their concentration is known to be equal to that of dissociable potassium chloride — an electrochemical potassium potential will be created between the systems (Boundless, 2020). This state of potassium ions stops when the same potassium concentration is created in the communicating systems, noting that the movement of the ions does not stop but no longer has a common direction (Soult, 2019). At the same time, chlorine anions prove incapable of penetrating through the membrane, and therefore no negative ion equilibrium will be established between these systems.
The situation, in this case, will be identical; only instead of potassium equilibrium, chlorine equilibrium will be reached. The chlorine ions will move along the concentration gradient, and their generalized movement will stop when the same concentration of chlorine exists in each of the two systems. The potassium ions will not be subject to movement because the semipermeable membrane cannot allow them to pass through. Consequently, equilibrium will exist only for chlorine ions but not for potassium ions in this case. It is essential that diffusion, in this case, is also not stopped because this process cannot stop spontaneously. Instead, chlorine ions will constantly move between systems without any organized movement.
References
Boundless. (2020). Osmosis. LibreTexts. Web.
Buckley, G. (2020). Concentration gradient. Biology Dictionary. Web.
Soult, A. (2019). Osmosis and diffusion. LibreTexts. Web.