Question

Define : Isotonic solution

Hint:

For competitive exams, remember that \( 0.9% \) (mass/volume) NaCl solution is isotonic with human blood. This is why saline drips are prepared at this specific concentration.

Answer 1

Step 1: Understanding the Concept:
Osmosis is the spontaneous flow of solvent molecules from a region of lower solute concentration to a region of higher solute concentration through a semipermeable membrane.
The pressure required to stop this flow is called osmotic pressure (\( \pi \)).
Step 2: Detailed Explanation:
When two solutions have exactly the same osmotic pressure, they are considered to be in osmotic equilibrium with each other.
This means that if these two solutions are separated by a semipermeable membrane, there will be no net movement of solvent between them because the "driving force" (osmotic pressure difference) is zero.
For dilute solutions of non-electrolytes at the same temperature \( T \), being isotonic implies they have the same molar concentration (\( M_1 = M_2 \)).
Step 3: Final Answer:
Isotonic solutions are solutions that exert the same osmotic pressure at the same temperature.