Assertion (A): The sum of mole fractions of all the component of a solution is unity.
Reason (R ): The mole fraction is a temperature dependent quantity.

Options

A. If both `(A)` and `(R )` are correct, and `(R )` is the correct explanation of `(A)`.
B. If both `(A)` and `(R )` are correct, but `(R )` is not the correct explanation of `(A)`.
C. If `(A)` is correct, but `(R )` is incorrect.
D. If `(A)` is incorrect, but `(R )` is correct.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that "The sum of mole fractions of all the components of a solution is unity."

- **Explanation**: In a solution, the mole fraction of each component is defined as the ratio of the number of moles of that component to the total number of moles of all components in the solution. If we have components A and B, the mole fractions can be represented as:
- Mole fraction of A (X_A) = n_A / (n_A + n_B)
- Mole fraction of B (X_B) = n_B / (n_A + n_B)

Therefore, the sum of the mole fractions is:
\[ X_A + X_B = \frac{n_A}{n_A + n_B} + \frac{n_B}{n_A + n_B} = \frac{n_A + n_B}{n_A + n_B} = 1 \]
- **Conclusion**: The assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "The mole fraction is a temperature-dependent quantity."

- **Explanation**: The mole fraction is calculated based on the number of moles of each component in a solution. It is given by:
\[ \text{Mole fraction} = \frac{\text{Number of moles of component}}{\text{Total number of moles of all components}} \]
This definition shows that the mole fraction depends solely on the amount of substance and not on temperature. Temperature may affect the solubility of a substance, but it does not change the mole fraction of a solution once the amounts are determined.
- **Conclusion**: The reason is **false**.

### Step 3: Final Conclusion
Since the assertion is true and the reason is false, the correct answer is that the assertion is correct, but the reason is incorrect.

### Answer:
The correct option is: Assertion is correct, but the reason is incorrect.

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