Question

Which of the following solutions is isotonic with human blood?

• A. \(0.1%\) NaCl solution
• B. \(0.5%\) NaCl solution
• C. \(0.9%\) NaCl solution
• D. \(2%\) NaCl solution

Hint:

Physiological saline or normal saline used in hospitals is: \[ 0.9% \text{ NaCl} \] because it is isotonic with human blood.

Answer 1

The Correct Option is C

Concept: An isotonic solution is a solution having the same osmotic pressure as the fluid inside human blood cells. In isotonic conditions:
• No net movement of water occurs.
• Blood cells neither shrink nor swell. Human blood plasma is isotonic with approximately: \[ 0.9% \text{ NaCl solution} \]

Step 1: Understand isotonicity.
If external solution concentration equals internal cell concentration: \[ \text{Water entering} = \text{Water leaving} \] Thus:
• Cell size remains unchanged.
• Osmotic equilibrium is maintained.

Step 2: Compare all options.

• \(0.1%\) NaCl: Hypotonic
• \(0.5%\) NaCl: Hypotonic
• \(0.9%\) NaCl: Isotonic
• \(2%\) NaCl: Hypertonic Thus only: \[ 0.9% \text{ NaCl} \] matches blood osmotic pressure.

Step 3: Write the final answer.
Hence, isotonic solution is: \[ \boxed{0.9% \text{ NaCl solution}} \] Therefore, the correct option is: \[ \boxed{(C)} \]