Among the metals `Cr,Fe,Mn,Ti,Ba`, and `Mg`, the one that cannot be obtained by reduction of metal oxide by aluminium is

Options

A. Cr
B. Fe
C. Mn
D. Mg

Answer

To solve the problem of identifying which metal among `Cr, Fe, Mn, Ti, Ba`, and `Mg` cannot be obtained by the reduction of its metal oxide using aluminum, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Reduction Process**: The reduction of metal oxides by aluminum is a thermite reaction where aluminum serves as a reducing agent. The general reaction can be represented as:
\[ \text{Metal Oxide} + \text{Aluminum} \rightarrow \text{Metal} + \text{Aluminum Oxide} \]

2. **Analyze Each Metal**:
- **Chromium (Cr)**:
\[ \text{Cr}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Cr} + \text{Al}_2\text{O}_3 \]
- This reaction occurs, so chromium can be obtained.

- **Iron (Fe)**:
\[ \text{Fe}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Fe} + \text{Al}_2\text{O}_3 \]
- This reaction occurs, so iron can be obtained.

- **Manganese (Mn)**:
\[ \text{MnO}_2 + 2\text{Al} \rightarrow \text{Mn} + \text{Al}_2\text{O}_3 \]
- This reaction occurs, so manganese can be obtained.

- **Barium (Ba)**:
\[ \text{BaO} + 2\text{Al} \rightarrow \text{Ba} + \text{Al}_2\text{O}_3 \]
- This reaction occurs, so barium can be obtained.

- **Magnesium (Mg)**:
\[ \text{MgO} + 2\text{Al} \rightarrow \text{No Reaction} \]
- There is no reaction between magnesium oxide and aluminum under normal conditions. Therefore, magnesium cannot be obtained by this method.

3. **Conclusion**: Among the metals listed, magnesium (Mg) is the one that cannot be obtained by the reduction of its oxide using aluminum.

### Final Answer:
The metal that cannot be obtained by reduction of metal oxide by aluminum is **Magnesium (Mg)**.

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