The metal that cannot be produced on reduction of its oxide by aluminium is :-

Options

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

Explanation

To determine the metal that cannot be produced by the reduction of its oxide using aluminum, we need to analyze the position of the metals in the electrochemical series and their oxidation potentials. Here’s a step-by-step solution:

### Step 1: Understand the Reduction Process
Reduction of metal oxides using aluminum involves a thermite reaction where aluminum acts as a reducing agent. The metal oxide is reduced to its elemental form, and aluminum is oxidized to aluminum oxide.

### Step 2: Review the Electrochemical Series
The electrochemical series ranks elements based on their standard electrode potentials. Metals that are higher in the series have a greater tendency to lose electrons (higher oxidation potential) and cannot be reduced by metals lower in the series.

### Step 3: Identify the Metals in the Options
The options given are:
1. Chromium
2. Manganese
3. Iron
4. Magnesium

### Step 4: Compare the Metals with Aluminum
- **Aluminum** is positioned in the electrochemical series below magnesium but above iron, manganese, and chromium.
- Metals that are above aluminum in the series (like magnesium) cannot be reduced by aluminum because they will oxidize instead.

### Step 5: Analyze Each Option
- **Chromium**: Can be reduced by aluminum.
- **Manganese**: Can be reduced by aluminum.
- **Iron**: Can be reduced by aluminum.
- **Magnesium**: Cannot be reduced by aluminum as it is above aluminum in the electrochemical series.

### Conclusion
The metal that cannot be produced by the reduction of its oxide using aluminum is **Magnesium**.

### Final Answer
**The correct option is: Magnesium (4th option).**

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