Assertion :- The freezing point is the temperature at which solid crystallizzes from solution.
Reason :- The freezing point depression is the difference between that temperature and freezing point of pure solvent.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

To analyze the assertion and reason provided in the question, we can break down the concepts step by step.

### Step 1: Understanding the Assertion
The assertion states: "The freezing point is the temperature at which solid crystallizes from solution."

**Explanation:**
- The freezing point of a solution is indeed the temperature at which the liquid phase transitions into the solid phase. This means that at this temperature, the solute and solvent begin to form a solid structure.

### Step 2: Understanding the Reason
The reason states: "The freezing point depression is the difference between that temperature and the freezing point of pure solvent."

**Explanation:**
- Freezing point depression refers to the phenomenon where the freezing point of a solution is lower than that of the pure solvent. This is quantified as:
\[ \Delta T_f = T_{f}^{0} - T_{f} \]
where:
- \( \Delta T_f \) is the freezing point depression,
- \( T_{f}^{0} \) is the freezing point of the pure solvent,
- \( T_{f} \) is the freezing point of the solution.

### Step 3: Conclusion
Both the assertion and the reason are correct. The freezing point is indeed the temperature at which a solid crystallizes from a solution, and the freezing point depression is the difference between the freezing point of the pure solvent and that of the solution.

### Final Answer
- **Assertion:** True
- **Reason:** True
- **Conclusion:** Both the assertion and reason are correct and related.

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