Hydrogen gas is not liberated when the following metal is added to dil. `HCl :`

Options

A. Ag
B. Zn
C. Mg
D. Sn

Explanation

To determine which metal does not liberate hydrogen gas when added to dilute hydrochloric acid (HCl), 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 can displace hydrogen from acids, while those that are less reactive cannot.

### Step 2: Identify the Metals in the Question
The metals given in the question are:
- Silver (Ag)
- Zinc (Zn)
- Magnesium (Mg)
- Tin (Sn)

### Step 3: Compare the Metals with Hydrogen in the Reactivity Series
- **Zinc (Zn)**: More reactive than hydrogen. It can displace hydrogen from HCl.
- **Magnesium (Mg)**: More reactive than hydrogen. It can displace hydrogen from HCl.
- **Tin (Sn)**: Slightly more reactive than hydrogen. It can also displace hydrogen from HCl.
- **Silver (Ag)**: Less reactive than hydrogen. It cannot displace hydrogen from HCl.

### Step 4: Conclusion
Since silver is below hydrogen in the reactivity series, it does not liberate hydrogen gas when added to dilute HCl. Therefore, the answer is silver.

### Final Answer:
**Silver (Ag) is the metal that does not liberate hydrogen gas when added to dilute HCl.**

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