Metal which does not react with cold water but evolves `H_(2)` with steam is `:`

Options

A. Na
B. Mg
C. Au
D. Fe

Explanation

To solve the question of identifying a metal that does not react with cold water but evolves hydrogen gas when reacting with steam, we can follow these steps:

### Step 1: Understand the Properties of Metals
Metals can react with water in different forms: cold water, hot water, and steam. The reactivity of metals with water varies, and some metals react only with steam.

### Step 2: Identify the Types of Reactions
- **Cold Water Reaction**: Some metals, like sodium and potassium, react vigorously with cold water.
- **Hot Water Reaction**: Metals like magnesium can react with hot water.
- **Steam Reaction**: Metals like iron (Fe), zinc (Zn), and aluminum (Al) can react with steam to produce hydrogen gas.

### Step 3: Analyze the Given Options
We need to find a metal that:
- Does **not** react with cold water.
- **Does** react with steam to produce hydrogen gas.

### Step 4: Evaluate Common Metals
- **Gold (Au)**: This is a noble metal and does not react with water in any form.
- **Iron (Fe)**: Reacts with steam to produce iron oxide and hydrogen.
- **Aluminum (Al)**: Also reacts with steam.
- **Zinc (Zn)**: Reacts with steam as well.

### Step 5: Conclusion
Among the metals listed, **iron (Fe)** is a suitable candidate as it does not react with cold water but does react with steam to produce hydrogen gas.

### Final Answer
The metal which does not react with cold water but evolves hydrogen with steam is **Iron (Fe)**.

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