In reaction of hydrogen peroxide and sodium carbonate, `H_2O_2` acts as____.

Explanation

To determine how hydrogen peroxide (H₂O₂) acts in the reaction with sodium carbonate (Na₂CO₃), we can analyze the chemical behavior of both substances involved in the reaction.

### Step-by-Step Solution:

1. **Identify the Nature of Sodium Carbonate (Na₂CO₃)**:
- Sodium carbonate is a basic salt. It can react with acids to produce carbon dioxide and a corresponding salt.

2. **Consider the Nature of Hydrogen Peroxide (H₂O₂)**:
- Hydrogen peroxide can act as an oxidizing agent, but in this context, we need to focus on its acid-base properties.

3. **Acid-Base Reaction**:
- In the presence of sodium carbonate, H₂O₂ behaves as an acid. This is because it can donate protons (H⁺ ions) to the basic sodium carbonate.

4. **Reaction Products**:
- The reaction between H₂O₂ and Na₂CO₃ leads to the formation of sodium peroxide (Na₂O₂) and carbonic acid (H₂CO₃).
- The reaction can be represented as:
\[ H_2O_2 + Na_2CO_3 \rightarrow Na_2O_2 + H_2CO_3 \]

5. **Decomposition of Carbonic Acid**:
- Carbonic acid (H₂CO₃) is unstable and decomposes into water (H₂O) and carbon dioxide (CO₂):
\[ H_2CO_3 \rightarrow H_2O + CO_2 \]
- The evolution of carbon dioxide gas can be observed in the reaction.

6. **Conclusion**:
- Therefore, in the reaction of hydrogen peroxide with sodium carbonate, H₂O₂ acts as an **acid**.

### Final Answer:
In the reaction of hydrogen peroxide and sodium carbonate, H₂O₂ acts as an **acid**.