During Hoope's process for eelctrolytic refining of Al, the middle layer is of

Options

A. Pure Al
B. Impure Al
C. Cryolite `+BaF_2`
D. Alloys of Al, Ca, Si

Answer

To solve the question regarding the middle layer during Hoopes' process for electrolytic refining of aluminum, we can follow these steps:

### Step 1: Understand Hoopes' Process
Hoopes' process is used for the electrolytic refining of aluminum. It involves the separation of aluminum from its ores using electrolysis. The process results in the formation of different layers based on the densities and compositions of the materials involved.

**Hint:** Research the basic principles of electrolytic refining to understand the separation of materials.

### Step 2: Identify the Layers
In Hoopes' process, there are three distinct layers formed during the electrolysis:
1. **Upper Layer:** This layer consists of pure molten aluminum.
2. **Middle Layer:** This layer is composed of molten fluorides.
3. **Lower Layer:** This layer contains impure aluminum.

**Hint:** Remember that the upper layer is always the pure product, while the lower layer contains impurities.

### Step 3: Analyze the Middle Layer Composition
The middle layer is specifically composed of molten fluorides, which typically include cryolite (Na3AlF6) and barium fluoride (BaF2). These compounds help in lowering the melting point and increasing the conductivity of the electrolyte.

**Hint:** Consider the role of cryolite and other fluorides in the electrolytic process.

### Step 4: Conclusion
Based on the analysis, the middle layer during Hoopes' process for electrolytic refining of aluminum is composed of cryolite and barium fluoride.

**Final Answer:** The middle layer is made of cryolite plus BaF2.

### Summary
- The upper layer contains pure molten aluminum.
- The middle layer consists of molten fluorides (cryolite and BaF2).
- The lower layer contains impure aluminum.

**Correct Option:** Cryolite plus BaF2 (Option 3).