Final answer:
Red blood cells in a 0.3 M NaCl solution will experience crenation due to the hypertonic nature of the solution causing water to move out of the cells.
Step-by-step explanation:
When red blood cells (RBCs) are placed in a 0.3 M NaCl solution, they will undergo crenation. This process happens because the external solution is hypertonic relative to the cytoplasm of the RBCs. A hypertonic solution, such as the 0.3 M NaCl, has a higher solute concentration than the inside of the cell, leading to the movement of water out of the red blood cells to balance solute concentrations on either side of the cell membrane.
This results in the cells shriveling up. The isotonic NaCl solution for red blood cells, which would cause no change in their shape, has an osmolarity of 0.32 osmol/L. Therefore, a hypertonic solution greater than 0.32 osmol/L (such as 0.3 M NaCl which is equivalent to 0.6 osmol/L since each unit of NaCl produces two ions) will cause crenation of the red blood cells.