Final answer:
Cells placed in a 0.9% NaCl (w/v) solution will maintain their normal volume and shape because the solution is isotonic. The cells will not undergo hemolysis or crenation as the osmotic conditions do not favor an influx or efflux of water to a degree that would cause a change in cell volume.
Step-by-step explanation:
When cells are placed in a 0.9% NaCl (w/v) solution, which is isotonic to the intracellular fluid of red blood cells, no net osmosis occurs, and therefore the cells maintain their normal volume and shape. This environment is isotonic because the osmolality of the solution is similar to that of the intracellular fluid. Red blood cell membranes are water permeable and will maintain normal volume and shape in an isotonic solution.
In contrast, cells would experience hemolysis in a hypotonic solution, where water would rush into the cells, causing them to swell and possibly burst. On the other hand, in a hypertonic solution, where the concentration of solutes is higher outside the cell, water would leave the cell, leading to crenation, where the cells shrivel and can become dysfunctional.