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 (H₂) when reacting with dilute hydrochloric acid (HCl), we can follow these steps:

### Step 1: Understanding the Reaction
When a metal reacts with dilute HCl, it typically displaces hydrogen from the acid, resulting in the formation of a metal chloride and the evolution of hydrogen gas. The general reaction can be represented as:
\[ \text{Metal (M)} + 2 \text{HCl} \rightarrow \text{Metal Chloride (MCl)} + \text{H}_2 \uparrow \]

### Step 2: Reactivity Series
The ability of a metal to displace hydrogen from acids is determined by its position in the reactivity series. Metals that are more reactive than hydrogen will displace hydrogen and evolve H₂ gas. Conversely, metals that are less reactive than hydrogen will not displace hydrogen and therefore will not evolve H₂ gas.

### Step 3: Identifying Non-Reactive Metals
The metals that do not evolve hydrogen gas with dilute HCl include:
1. **Platinum (Pt)**
2. **Silver (Ag)**
3. **Gold (Au)**
4. **Copper (Cu)**
5. **Mercury (Hg)**

These metals are located below hydrogen in the reactivity series, indicating that they are less reactive and will not displace hydrogen from dilute acids.

### Step 4: Conclusion
Thus, the metals that will not evolve hydrogen gas when treated with dilute HCl are:
- Platinum (Pt)
- Silver (Ag)
- Gold (Au)
- Copper (Cu)
- Mercury (Hg)