Metals which will not evolve `H_2` gas with dil. HCl are

Options

A. cu, Ag, Au
B. Cu, Zn , Al
C. Fe, Ag , Pt
D. Hg , Mg , Pt

Answer

To determine which metals will not evolve hydrogen gas when reacting with dilute hydrochloric acid (HCl), we need to refer to the electrochemical series. This series ranks metals based on their ability to displace hydrogen from acids.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When metals react with dilute HCl, they can either evolve hydrogen gas (H2) or not, depending on their position in the electrochemical series.
- Metals above hydrogen in the series can displace hydrogen and will evolve H2 gas.

2. **Identifying Metals**:
- The question lists several metals, and we need to determine their positions relative to hydrogen in the electrochemical series.

3. **Analyzing Each Metal**:
- **Copper (Cu)**: Located below hydrogen in the electrochemical series. It will not evolve hydrogen gas with dilute HCl.
- **Silver (Ag)**: Also below hydrogen. It will not evolve hydrogen gas with dilute HCl.
- **Gold (Au)**: Similarly, it is below hydrogen and will not evolve hydrogen gas with dilute HCl.
- **Zinc (Zn)**: Above hydrogen in the electrochemical series. It will evolve hydrogen gas with dilute HCl.
- **Aluminum (Al)**: Above hydrogen. It will evolve hydrogen gas with dilute HCl.
- **Iron (Fe)**: Above hydrogen. It will evolve hydrogen gas with dilute HCl.
- **Mercury (Hg)**: Below hydrogen. It will not evolve hydrogen gas with dilute HCl.
- **Magnesium (Mg)**: Above hydrogen. It will evolve hydrogen gas with dilute HCl.
- **Platinum (Pt)**: Below hydrogen. It will not evolve hydrogen gas with dilute HCl.

4. **Conclusion**:
- The metals that will not evolve hydrogen gas with dilute HCl are: **Copper (Cu), Silver (Ag), Gold (Au), Mercury (Hg), and Platinum (Pt)**.

### Final Answer:
The metals which will not evolve H2 gas with dilute HCl are **Cu, Ag, Au, Hg, and Pt**.