Which one of the following material conducts electicity ?

Options

A. Diamond
B. Crystalline NaCl
C. Barium sulphate
D. Fused KCl

Answer

To determine which of the following materials conducts electricity, we need to analyze each option based on the presence of free ions or electrons, as these are necessary for electrical conductivity.

### Step-by-Step Solution:

1. **Understanding Electrical Conductivity**:
- Electrical conductivity in materials is primarily due to the presence of free-moving charged particles, which can be either electrons or ions.

2. **Analyzing Diamond**:
- Diamond is an allotrope of carbon with a tetrahedral structure. In this structure, all carbon atoms are covalently bonded to four other carbon atoms, resulting in no free electrons or ions.
- **Conclusion**: Diamond does not conduct electricity.

3. **Analyzing Crystalline NaCl**:
- Crystalline NaCl (sodium chloride) is a solid at room temperature. In its solid state, the ions (Na⁺ and Cl⁻) are fixed in a lattice structure and cannot move freely.
- **Conclusion**: Crystalline NaCl does not conduct electricity in solid form. However, when melted (fused), the ions become mobile, allowing it to conduct electricity.

4. **Analyzing Barium Sulphate (BaSO₄)**:
- Barium sulphate is a precipitate (PPT) and is also a solid. In this form, it does not have free ions available for conduction.
- **Conclusion**: Barium sulphate does not conduct electricity.

5. **Analyzing Fused KCl**:
- Fused KCl (potassium chloride) is obtained by melting solid KCl. In this molten state, the K⁺ and Cl⁻ ions are free to move, which allows the material to conduct electricity.
- **Conclusion**: Fused KCl conducts electricity due to the presence of free ions.

### Final Answer:
Among the given options, **fused KCl** is the material that conducts electricity.

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