Final answer:
A 150 mM solution of NaCl is not universally isotonic; it depends on the comparison to body fluid osmolarity. Isotonic solutions have the same osmolarity as the body's cells, typically around 300 mOsm. A 150 mM solution of NaCl results in 300 mOsm, which is isotonic if the osmolarity of body fluids is used as a reference.
Step-by-step explanation:
The statement 'A 150 mM solution of NaCl is isotonic' can be false depending on the comparison being made with the osmolarity of body fluids. An isotonic solution has an osmolarity that matches that of the body's cells, typically around 300 mOsm. NaCl dissociates into two ions, sodium (Na+) and chloride (Cl-), when dissolved. Therefore, a 150 mM NaCl solution will have an osmolarity of 300 mOsm (150 mM × 2), which technically is isotonic. However, typical isotonic solutions that are used in medical contexts are 0.9% m/v NaCl solutions. As such, asserting the isotonic nature of a solution solely based on its molarity without considering the particular medical context and the actual comparison with the osmolarity of body fluids can be misleading.
Cells in an isotonic solution experience no net movement of water, maintaining their normal shape and volume. In contrast, cells in a hypotonic solution will swell as water enters the cell to equalize the solute concentration, which can lead to lysis (bursting). In a hypertonic solution, cells will shrink as water moves out of them, a process known as crenation. The osmolarity of body fluids is typically around 300 mOsm, which is matched by isotonic solutions of either 0.9% m/v NaCl or 5% m/v glucose.