The quantity remaining constant on dilution is

Options

A. Number of moles of solute
B. Molarity of the solution
C. Mole fraction of solute
D. Mass of the solution

Answer

To solve the question, "The quantity remaining constant on dilution is," we need to analyze the concept of dilution in chemistry.

### Step-by-Step Solution:

1. **Understanding Dilution**:
- Dilution is the process of reducing the concentration of a solute in a solution, usually by adding more solvent.

2. **Concept of Concentration**:
- Concentration is defined as the amount of solute divided by the volume of the solution. Mathematically, it can be expressed as:
\[ \text{Concentration (C)} = \frac{\text{Number of moles of solute (n)}}{\text{Volume of solution (V)}} \]

3. **Effect of Dilution on Concentration**:
- When we dilute a solution, we increase the volume (V) of the solution. According to the formula, if the volume increases while the number of moles of solute remains constant, the concentration will decrease.

4. **Number of Moles of Solute**:
- The number of moles of solute (n) does not change during dilution. It remains constant regardless of how much solvent is added to the solution.

5. **Conclusion**:
- Therefore, the quantity that remains constant during dilution is the number of moles of solute.

### Final Answer:
The quantity remaining constant on dilution is the **number of moles of solute**.

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