What Liso value is used for uni-univalent electrolytes in isotonicity calculations?

• A. 3.4
• B. 1.0
• C. 2.0
• D. 4.0

Answer: (A)

Isotonicity calculations turn on how much a solute actually contributes to the solution’s osmotic pressure, which depends on how the solute dissociates. Liso is a practical factor used to convert the amount of solute into its osmotic contribution, taking into account dissociation and real‑world behavior in solution. For uni-univalent electrolytes (salts that dissociate into two ions), the standard Liso value used is 3.4. This empirical factor provides a reliable estimate of the osmotic effect of salts like NaCl when you’re calculating how much solute is needed to reach isotonicity. Non-electrolytes, which don’t dissociate, use 1.0, while the other numerical options don’t reflect the established adjustment used for these salts, so they wouldn’t give the correct isotonic approximation.