Which of the following solid has maximum melting points?

Options

A. `NaCl`
B. Ice
C. Dry ice
D. `SiO_(2)`

Answer

To determine which of the given solids has the maximum melting point, we will analyze the melting points of each solid mentioned in the question.

### Step-by-Step Solution:

1. **Identify the Solids**: The solids mentioned are NaCl (sodium chloride), ice (H2O), dry ice (solid CO2), and SiO2 (silicon dioxide).

2. **Analyze NaCl**:
- NaCl is an ionic solid with a rock salt structure.
- It has a high melting point due to strong ionic bonds between Na+ and Cl- ions.
- The melting point of NaCl is approximately 801 °C.

3. **Analyze Ice (H2O)**:
- Ice is a molecular solid.
- It has a melting point of 0 °C, which is relatively low compared to ionic and covalent solids.

4. **Analyze Dry Ice (Solid CO2)**:
- Dry ice is also a molecular solid.
- It has a melting point of about -78.5 °C, which is much lower than that of NaCl and ice.

5. **Analyze SiO2**:
- SiO2 is a covalent network solid, similar to diamond.
- It has a very high melting point due to the strong covalent bonds in its giant structure.
- The melting point of SiO2 is approximately 1710 °C.

6. **Comparison of Melting Points**:
- NaCl: 801 °C
- Ice: 0 °C
- Dry Ice: -78.5 °C
- SiO2: 1710 °C

7. **Conclusion**:
- Among the solids analyzed, SiO2 has the highest melting point.

### Final Answer:
SiO2 (silicon dioxide) has the maximum melting point among the given solids.

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