Select correct answers from the choices A, B, C, D which are given. Write down only the letter corresponding to the correct answer.
Which metal liberates hydrogen gas from acid and base both? Cu, Zn, Fe, Ca

Options

A. Cu
B. Zn
C. Fe
D. Ca

Answer

To solve the question, we need to determine which metal from the given options can liberate hydrogen gas when it reacts with both acids and bases.

### Step-by-Step Solution:

1. **Identify the Metals:**
The metals given in the options are:
- A. Copper (Cu)
- B. Zinc (Zn)
- C. Iron (Fe)
- D. Calcium (Ca)

2. **Understand the Reactions:**
- **Acid Reaction:** Metals can react with acids to produce hydrogen gas and a salt.
- **Base Reaction:** Metals can also react with bases to produce hydrogen gas and a different type of salt.

3. **Analyze Each Metal:**
- **Copper (Cu):**
- Copper does not react with dilute acids to liberate hydrogen gas. It is less reactive and does not react with bases either.
- **Zinc (Zn):**
- Zinc reacts with hydrochloric acid (HCl) to produce zinc chloride (ZnCl2) and hydrogen gas (H2).
- Zinc also reacts with sodium hydroxide (NaOH) to produce sodium zincate (Na2ZnO2) and hydrogen gas (H2).
- **Iron (Fe):**
- Iron reacts with acids to produce hydrogen gas, but it does not react with all bases to liberate hydrogen gas.
- **Calcium (Ca):**
- Calcium reacts with acids to produce hydrogen gas and calcium salt, and it reacts with water (which can be considered a base) to produce hydrogen gas. However, it does not react with all bases.

4. **Conclusion:**
After analyzing the reactions of each metal, we find that only **Zinc (Zn)** liberates hydrogen gas when reacting with both acids and bases.

### Final Answer:
**B**

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