Question

If the intracellular concentration of NaCl is 1%, then which solution is hypotonic to the cell?

• A. 0.1N
• B. 0.2N
• C. 0.3N
• D. 0.4N

Hint:

Hypo = Low (Solute).
Hyper = High (Solute).
Iso = Equal.
If you put a cell in a Hypotonic solution, the cell will swell like a Hippo!

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks to identify a "hypotonic" solution relative to a cell containing 1% NaCl. A hypotonic solution has a lower solute concentration than the cell, causing water to enter the cell by osmosis.
Key Formula or Approach:
We must first convert the percentage concentration of the intracellular fluid into Normality ($N$) to compare it with the given options.
\[ \text{Normality (N)} = \frac{\text{Mass (g)}}{\text{Eq. weight} \times \text{Volume (L)}} \]

Step 2: Detailed Explanation:

• Converting 1% NaCl to g/L: 1% means $1$ gram of NaCl in $100$ mL of solution.
Therefore, in $1000$ mL ($1$ Liter), there is $10$ grams of NaCl.

• Calculating Molarity/Normality:
- Molecular Weight of NaCl $\approx 58.5$ g/mol.
- Since NaCl dissociates into one $Na^+$ and one $Cl^-$, its equivalent weight is the same as its molecular weight ($58.5$).
- $\text{Normality} = 10 / 58.5 \approx 0.171 N$.

• Intracellular Tonicity: The cell's internal environment is approximately 0.17 N.

• Definition of Hypotonic: A solution is hypotonic if its concentration is less than $0.17 N$.

• Evaluating Options:
- (A) 0.1N: $0.1 < 0.17$. This is hypotonic.
- (B) 0.2N: $0.2 > 0.17$. This is hypertonic.
- (C) 0.3N: Hypertonic.
- (D) 0.4N: Hypertonic.

Step 3: Final Answer:
A $0.1N$ solution has a lower concentration of solute than the intracellular $1\%$ ($0.17N$) NaCl concentration and is therefore hypotonic to the cell.