Which of the following is not a mixture?

Options

A. Sodium chloride solution
B. Brass
C. Bronze
D. Molten sodium chloride

Explanation

To determine which of the following is not a mixture, we need to understand what a mixture is. A mixture consists of two or more substances that are combined physically but not chemically. This means that the individual components retain their own properties and can be separated by physical means.

### Step-by-Step Solution:

1. **Define Mixture**: A mixture is a combination of two or more substances that are not chemically bonded. The components can be elements or compounds.

2. **Analyze the Options**:
- **Option 1: Sodium Chloride Solution**: Sodium chloride (NaCl) is a compound. When dissolved in water, it forms a solution, which is a mixture of sodium chloride and water. Therefore, this is a mixture.

- **Option 2: Brass**: Brass is an alloy, which is a homogeneous mixture of metals (primarily copper and zinc). Since it is a mixture of metals, this is also a mixture.

- **Option 3: Bronze**: Similar to brass, bronze is an alloy made primarily of copper and tin. It is also a homogeneous mixture, so this is a mixture as well.

- **Option 4: Molten Sodium Chloride**: When sodium chloride is in a molten state, it is not mixed with any other substance. It is simply sodium chloride in a different physical state (liquid). Therefore, it is a compound, not a mixture.

3. **Conclusion**: Based on the analysis, the only option that is not a mixture is **molten sodium chloride**.

### Final Answer:
**Molten sodium chloride is not a mixture.**

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