Which one of the following metals will not liberate hydrogen gas when treated with dilute hydrochloric acid?

Options

A. Magnesium
B. Zinc
C. Copper
D. Iron

Explanation

To determine which metal will not liberate hydrogen gas when treated with dilute hydrochloric acid, we can follow these steps:

### Step 1: Understand the Reactivity Series
The reactivity series is a list of metals arranged in order of decreasing reactivity. Metals that are more reactive than hydrogen will displace hydrogen from acids, while those that are less reactive will not.

### Step 2: Identify the Position of Metals in the Reactivity Series
We need to identify where the given metals are located in the reactivity series. The metals typically considered in this context are:
- Lithium
- Potassium
- Barium
- Calcium
- Sodium
- Magnesium
- Aluminium
- Manganese
- Zinc
- Iron
- Copper
- Mercury
- Silver
- Gold

### Step 3: Compare Metals with Hydrogen
In the reactivity series, hydrogen is positioned between metals like zinc and copper. Metals above hydrogen will liberate hydrogen gas when reacting with dilute hydrochloric acid, while those below will not.

### Step 4: Analyze the Given Metals
Let’s analyze the metals:
- **Copper (Cu)**: Located below hydrogen in the reactivity series.
- **Zinc (Zn)**: Located above hydrogen, will liberate hydrogen.
- **Iron (Fe)**: Located above hydrogen, will liberate hydrogen.
- **Magnesium (Mg)**: Located above hydrogen, will liberate hydrogen.

### Step 5: Conclusion
Among the metals listed, **Copper** is the only metal that will not liberate hydrogen gas when treated with dilute hydrochloric acid.

### Final Answer
**Copper** will not liberate hydrogen gas when treated with dilute hydrochloric acid.

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