Which one of the following elements will not react with diluet HCI to produce `H_(2)`

Options

A. Hg
B. AI
C. Mg
D. Fe

Answer

To determine which element will not react with dilute HCl to produce hydrogen gas (H₂), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Reaction**: When a metal reacts with dilute hydrochloric acid (HCl), it can displace hydrogen gas if the metal is more reactive than hydrogen. The general reaction can be represented as:
\[ \text{Metal} + \text{HCl} \rightarrow \text{Metal Chloride} + \text{H}_2 \]

2. **Identify the Reactivity Series**: The reactivity series ranks metals based on their ability to displace hydrogen from acids. The series from most reactive to least reactive includes:
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminum (Al)
- Zinc (Zn)
- Iron (Fe)
- Tin (Sn)
- Lead (Pb)
- Hydrogen (H)
- Copper (Cu)
- Silver (Ag)
- Gold (Au)
- Mercury (Hg)

3. **Locate Hydrogen in the Series**: Hydrogen is positioned in the middle of the reactivity series. Metals that are more reactive than hydrogen will react with dilute HCl to produce H₂, while those that are less reactive will not.

4. **Analyze the Given Options**: We need to identify which element from the options provided is less reactive than hydrogen. According to the reactivity series:
- Metals like magnesium, aluminum, iron, and zinc are more reactive than hydrogen and will produce H₂ when reacting with dilute HCl.
- Metals like copper, silver, gold, and mercury are less reactive than hydrogen and will not produce H₂ when reacting with dilute HCl.

5. **Conclusion**: Among the elements listed, mercury (Hg) is less reactive than hydrogen. Therefore, it will not react with dilute HCl to produce hydrogen gas.

### Final Answer:
**Mercury (Hg) will not react with dilute HCl to produce H₂.**