Which of the following is correct ?

Options

A. The sum of mole fractions of all the components in a solution is always unity
B. Mole fraction depends upon temperature
C. Mole fraction is always negative
D. Mole fraction is independent of content of solute in solution

Answer

To solve the question regarding the correctness of the statements about mole fraction, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Mole Fraction**:
- Mole fraction (denoted as \( \mu \)) is defined as the ratio of the number of moles of a component to the total number of moles of all components in a solution.
- For a solution with components A (solute) and B (solvent), the mole fractions are defined as:
\[ \mu_A = \frac{n_A}{n_A + n_B} \]
\[ \mu_B = \frac{n_B}{n_A + n_B} \]

2. **Sum of Mole Fractions**:
- The sum of the mole fractions of all components in a solution can be calculated as:
\[ \mu_A + \mu_B = \frac{n_A}{n_A + n_B} + \frac{n_B}{n_A + n_B} = \frac{n_A + n_B}{n_A + n_B} = 1 \]
- This shows that the sum of mole fractions is always unity.

3. **Analyzing Each Statement**:
- **Option A**: "The sum of mole fractions of all the components in a solution is always unity."
- This statement is **correct** as shown in the previous step.

- **Option B**: "Mole fraction depends upon temperature."
- This statement is **incorrect**. Mole fraction is a ratio of moles, and the number of moles does not change with temperature. Therefore, mole fraction is independent of temperature.

- **Option C**: "Mole fraction is always negative."
- This statement is **incorrect**. The number of moles is always positive, hence mole fraction, being a ratio of positive quantities, is also always positive.

- **Option D**: "Mole fraction is independent of the content of solute in solution."
- This statement is **incorrect**. The mole fraction of a component does depend on the number of moles of that component, which includes the solute.

4. **Conclusion**:
- The only correct statement among the options provided is **Option A**: "The sum of mole fractions of all the components in a solution is always unity."

### Final Answer:
The correct option is **A**.