The gas liberated when a metal is treated with acid or base

Options

A. oxygen
B. nitrogen
C. chlorine
D. hydrogen

Explanation

To determine the gas liberated when a metal is treated with an acid or base, we can analyze the reactions that occur in both scenarios.

### Step-by-Step Solution:

1. **Understanding the Reaction with Acids:**
- When a metal reacts with a dilute acid (like hydrochloric acid, HCl, or sulfuric acid, H2SO4), the general reaction can be represented as:
\[ \text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{Hydrogen gas} \]
- For example, when zinc reacts with hydrochloric acid:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \]
- Here, hydrogen gas (H2) is liberated.

2. **Understanding the Reaction with Bases:**
- Similarly, when a metal reacts with a strong base (like sodium hydroxide, NaOH, or potassium hydroxide, KOH), the reaction can be represented as:
\[ \text{Metal} + \text{Base} \rightarrow \text{Salt} + \text{Hydrogen gas} \]
- For instance, when aluminum reacts with sodium hydroxide:
\[ 2\text{Al} + 2\text{NaOH} + 6\text{H}_2\text{O} \rightarrow 2\text{NaAl(OH)}_4 + 3\text{H}_2 \uparrow \]
- Again, hydrogen gas (H2) is produced.

3. **Identifying the Gas:**
- From both reactions, it is clear that the gas liberated when a metal reacts with either an acid or a base is hydrogen gas (H2).

4. **Conclusion:**
- Therefore, the correct answer to the question is:
- **Option D: Hydrogen**