Assertion : Molar mass of `D_(2)O` is more than than of protium oxide.
Reason : Boiling point of protium oxide is higher than that of `D_(2)O`.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.

Answer

To solve the given question, we will analyze both the assertion and the reason step by step.

### Step 1: Analyze the Assertion
**Assertion:** The molar mass of D₂O is more than that of protium oxide (H₂O).

- **Calculation of Molar Mass of D₂O:**
- D₂O (Deuterium oxide) consists of 2 deuterium atoms and 1 oxygen atom.
- Molar mass of deuterium (D) = 2 g/mol.
- Molar mass of oxygen (O) = 16 g/mol.
- Therefore, molar mass of D₂O = (2 × 2) + 16 = 4 + 16 = 20 g/mol.

- **Calculation of Molar Mass of H₂O:**
- H₂O (Protium oxide) consists of 2 hydrogen atoms and 1 oxygen atom.
- Molar mass of hydrogen (H) = 1 g/mol.
- Therefore, molar mass of H₂O = (2 × 1) + 16 = 2 + 16 = 18 g/mol.

- **Comparison:**
- Molar mass of D₂O = 20 g/mol.
- Molar mass of H₂O = 18 g/mol.
- Since 20 g/mol > 18 g/mol, the assertion is **true**.

### Step 2: Analyze the Reason
**Reason:** The boiling point of protium oxide (H₂O) is higher than that of D₂O.

- **Boiling Points:**
- The boiling point of H₂O (protium oxide) is approximately 100°C.
- The boiling point of D₂O (deuterium oxide) is approximately 101.4°C.

- **Comparison:**
- Since the boiling point of D₂O (101.4°C) is higher than that of H₂O (100°C), the reason is **false**.

### Conclusion
- The assertion is true, but the reason is false. Therefore, the correct option is:
**Option C: Assertion is true but the reason is false.**

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