A beaker of water is separated by a selectively permeable membrane that allows the passage of water but not ions. A solution of 4% sodium chloride (NaCl) is placed on one side of the membrane and pure water is placed on the other side of the membrane. The solutions are allowed to equilibrate. At this point, which process is going on

osmosis

Explanation:

The process that was going is osmosis.

Osmosis is the movement of water molecules from regions of high water potential to regions of low water potentials through a selectively permeable membrane.

In this case, the membrane is only permeable to water movement and not ions and water molecules move from the side with pure water (which happens to have higher water potential) to the side with 4% sodium chloride until equilibrium in water potential is established between the two sides.