The reaction between which of the following reactants produces hydrogen?

Options

A. Zn + HCl
B. `BaO_(2) + HCl`
C. `K_(2)S_(2)O_(8)+ H_(2)O`
D. `Na_(2)O_(2) + HCl`

Answer

To determine which reaction produces hydrogen gas, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Option 1: Zinc with HCl**
- When zinc (Zn) reacts with hydrochloric acid (HCl), the reaction is:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \]
- In this reaction, zinc displaces hydrogen from hydrochloric acid, resulting in the liberation of hydrogen gas (H₂).
- **Conclusion:** This option produces hydrogen gas.

2. **Option 2: Barium Peroxide with HCl**
- The reaction between barium peroxide (BaO₂) and hydrochloric acid (HCl) can be represented as:
\[ \text{BaO}_2 + 2\text{HCl} \rightarrow \text{BaCl}_2 + \text{H}_2\text{O}_2 \]
- Here, hydrogen peroxide (H₂O₂) is formed, but no hydrogen gas is liberated.
- **Conclusion:** This option does not produce hydrogen gas.

3. **Option 3: Potassium Persulfate with Water**
- The reaction of potassium persulfate (K₂S₂O₈) with water (H₂O) is:
\[ \text{K}_2\text{S}_2\text{O}_8 + 2\text{H}_2\text{O} \rightarrow 2\text{KHSO}_4 + \text{H}_2\text{O}_2 \]
- This reaction also produces hydrogen peroxide (H₂O₂) and does not liberate hydrogen gas.
- **Conclusion:** This option does not produce hydrogen gas.

4. **Option 4: Sodium Peroxide with HCl**
- The reaction between sodium peroxide (Na₂O₂) and hydrochloric acid (HCl) is:
\[ \text{Na}_2\text{O}_2 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{O}_2 \]
- Similar to the previous reactions, this produces hydrogen peroxide (H₂O₂) and does not liberate hydrogen gas.
- **Conclusion:** This option does not produce hydrogen gas.

### Final Answer:
The only reaction that produces hydrogen gas is **Option 1: Zinc with HCl**.