Which is true statement about `D_(2)O` and `H_(2)O` ?

Options

A. `D_(2)O` has lower dielectric constant than `H_(2)O`
B. NaCl is more solube in `D_(2)O` than in `H_(2)O`
C. both are correct
D. none is correct

Explanation

To determine which statement is true about D₂O (heavy water) and H₂O (normal water), we will analyze the properties of both substances, particularly focusing on their dielectric constants and solubility characteristics.

### Step-by-Step Solution:

1. **Understanding Dielectric Constant**:
- The dielectric constant is a measure of a substance's ability to insulate charges from each other. A higher dielectric constant indicates a better ability to dissolve ionic compounds.

2. **Dielectric Constants of H₂O and D₂O**:
- The dielectric constant of H₂O (normal water) is approximately 78.39.
- The dielectric constant of D₂O (heavy water) is approximately 78.06.
- Since 78.39 > 78.06, this indicates that H₂O has a higher dielectric constant than D₂O.

3. **Implications of Dielectric Constant**:
- Because H₂O has a higher dielectric constant, it is a better solvent for ionic compounds compared to D₂O. This means that substances like NaCl (sodium chloride) are more soluble in H₂O than in D₂O.

4. **Evaluating Statements**:
- The first statement claims that "D₂O has a lower dielectric constant than H₂O." This is true based on our findings.
- The second statement claims that "NaCl is more soluble in D₂O." This is false since we established that NaCl is more soluble in H₂O due to its higher dielectric constant.

5. **Conclusion**:
- The only true statement is that "D₂O has a lower dielectric constant than H₂O." Therefore, the correct answer is option A.

### Final Answer:
The true statement about D₂O and H₂O is: **D₂O has a lower dielectric constant than H₂O.**

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