`MgO` can be used as a refractory material because

Options

A. It is a good electrical insulator
B. It is a good conductor of heat
C. It has high melting point
D. None of the above

Answer

To determine why magnesium oxide (MgO) can be used as a refractory material, we need to analyze its properties and characteristics. Here's a step-by-step solution:

### Step 1: Understand Refractory Materials
Refractory materials are substances that can withstand high temperatures without melting or breaking down. They are used in furnaces, kilns, and reactors.

**Hint:** Refractory materials must have high melting points and good thermal stability.

### Step 2: Identify the Properties of MgO
Magnesium oxide (MgO) is known for several key properties:
- It has a very high melting point (over 2800 °C).
- It is a poor electrical conductor, making it a good electrical insulator.
- It has good thermal conductivity.

**Hint:** Focus on the melting point and electrical conductivity when considering its suitability as a refractory material.

### Step 3: Analyze the Options Given
The question provides four options regarding the properties of MgO:
1. It is a good electrical insulator.
2. It is a good conductor of heat.
3. It has a high melting point.
4. None of the above.

**Hint:** Evaluate each option based on the properties of MgO.

### Step 4: Evaluate Each Option
- **Option 1:** MgO is indeed a good electrical insulator due to its poor electrical conductivity.
- **Option 2:** This option is incorrect; MgO is not a good conductor of heat compared to metals, but it does have some thermal conductivity.
- **Option 3:** MgO has a very high melting point, which is a key reason for its use as a refractory material.
- **Option 4:** This option is incorrect since options 1 and 3 are valid.

**Hint:** Remember that for a material to be classified as refractory, it must have both high melting points and insulating properties.

### Step 5: Conclusion
Based on the analysis, the correct reasons why MgO can be used as a refractory material are:
- It has a high melting point.
- It is a good electrical insulator.

Thus, the correct options are 1 and 3.

**Final Answer:** MgO can be used as a refractory material because it has a high melting point and is a good electrical insulator.