Which of the following electropositive metal is used for the isolation of boron from `B_2O_3`?

Options

A. `Al`
B. `Zn`
C. `Mg`
D. `Au`

Answer

To determine which electropositive metal is used for the isolation of boron from \( B_2O_3 \), let's analyze the options step by step.

### Step 1: Understand the Reaction
Boron can be isolated from its oxide \( B_2O_3 \) through a reduction process. This involves using a more electropositive metal that can displace boron from its oxide.

### Step 2: Identify Electropositive Metals
Electropositive metals are those that readily lose electrons to form positive ions. Common examples include aluminum (Al), magnesium (Mg), sodium (Na), and calcium (Ca).

### Step 3: Evaluate the Reaction with Aluminum
When \( B_2O_3 \) reacts with aluminum, the reaction can be represented as:
\[ B_2O_3 + 6Al \rightarrow 2Al_2O_3 + 2B \]
This reaction produces aluminum oxide and crystalline boron. However, while aluminum can reduce \( B_2O_3 \), it is not the most efficient method.

### Step 4: Evaluate the Reaction with Magnesium
When \( B_2O_3 \) reacts with magnesium, the reaction can be represented as:
\[ B_2O_3 + 3Mg \rightarrow 3MgO + 2B \]
This reaction produces magnesium oxide and amorphous boron, which is often purer than the boron produced with aluminum.

### Step 5: Conclusion
Based on the reactions evaluated, magnesium is the more effective and preferred electropositive metal for the isolation of boron from \( B_2O_3 \).

### Final Answer
The correct electropositive metal used for the isolation of boron from \( B_2O_3 \) is **magnesium (Mg)**.

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