Which can't displace hydrogen from the compounds?

Options

A. Hg
B. Zn
C. Fe
D. None of these

Answer

To determine which metal cannot displace hydrogen from its compounds, we need to analyze the reactivity of the given metals: mercury (Hg), zinc (Zn), and iron (Fe).

### Step-by-Step Solution:

1. **Understanding Displacement Reactions**:
- A metal can displace hydrogen from its compounds if it is more reactive than hydrogen.

2. **Referencing the Reactivity Series**:
- The reactivity series is a list of metals arranged in order of decreasing reactivity. Metals higher in the series can displace those lower in the series from their compounds.

3. **Identifying the Position of Metals**:
- In the reactivity series:
- **Zinc (Zn)** is positioned above hydrogen, indicating that it is more reactive than hydrogen.
- **Iron (Fe)** is also positioned above hydrogen, meaning it is more reactive than hydrogen.
- **Mercury (Hg)** is positioned below hydrogen, indicating that it is less reactive than hydrogen.

4. **Conclusion**:
- Since zinc and iron are more reactive than hydrogen, they can displace hydrogen from its compounds.
- Mercury, being less reactive than hydrogen, cannot displace hydrogen from its compounds.

5. **Final Answer**:
- The metal that cannot displace hydrogen from its compounds is **mercury (Hg)**.