Which of the following has lower value of `D_(2)O` than for `H_(2)O` ?

Options

A. Molecular mass
B. Dielectric constant
C. Ionsization constant
D. Viscosity

Answer

To solve the question "Which of the following has lower value of D₂O than for H₂O?", we need to analyze the properties of deuterium oxide (D₂O) compared to regular water (H₂O).

### Step-by-Step Solution:

1. **Understanding the Compounds**:
- D₂O (deuterium oxide) is water where the hydrogen atoms are replaced by deuterium, an isotope of hydrogen.
- H₂O (water) consists of two hydrogen atoms and one oxygen atom.

2. **Molecular Mass Calculation**:
- Calculate the molecular mass of D₂O:
- D (deuterium) has an atomic mass of approximately 2 u.
- O (oxygen) has an atomic mass of approximately 16 u.
- Molecular mass of D₂O = (2 × 2) + 16 = 20 u.
- Calculate the molecular mass of H₂O:
- H (hydrogen) has an atomic mass of approximately 1 u.
- Molecular mass of H₂O = (2 × 1) + 16 = 18 u.

3. **Comparing Properties**:
- The question asks for properties where D₂O has a lower value than H₂O. The properties to consider are:
- Dielectric constant
- Ionization constant
- Viscosity
- Molecular mass

4. **Analyzing Each Property**:
- **Molecular Mass**: D₂O (20 u) is greater than H₂O (18 u). So, this is not a valid option.
- **Dielectric Constant**: D₂O has a lower dielectric constant compared to H₂O. This is a valid option.
- **Ionization Constant**: D₂O has a lower ionization constant than H₂O. This is also a valid option.
- **Viscosity**: D₂O has a higher viscosity than H₂O. This is not a valid option.

5. **Conclusion**:
- The properties where D₂O has a lower value than H₂O are the dielectric constant and the ionization constant.

### Final Answer:
The correct options are:
- Dielectric constant
- Ionization constant