`NaHCO_(3)` can be used to-

Options

A. Decrease acidity of stomach
B. Prepare `CO_(2)` used as fire extinguisher
C. Prepare bread
D. All of these

Answer

To solve the question regarding the uses of sodium bicarbonate (NaHCO₃), we will break down the information step by step.

### Step-by-Step Solution:

1. **Identify Sodium Bicarbonate**:
- Sodium bicarbonate is chemically represented as NaHCO₃. It is commonly known as baking soda.

**Hint**: Remember that sodium bicarbonate is a base and has various applications due to its chemical properties.

2. **Reaction with Acids**:
- Sodium bicarbonate reacts with acids to produce salt, water, and carbon dioxide (CO₂). This reaction can be represented as:
\[ \text{NaHCO}_3 + \text{Acid} \rightarrow \text{Salt} + \text{H}_2\text{O} + \text{CO}_2 \]

**Hint**: This reaction is important because it shows how NaHCO₃ can neutralize acids.

3. **Use in Decreasing Stomach Acidity**:
- When sodium bicarbonate is ingested, it reacts with the hydrochloric acid (HCl) in the stomach. This reaction helps to neutralize excess stomach acid, providing relief from acidity.
- The reaction can be summarized as:
\[ \text{NaHCO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O} + \text{CO}_2 \]

**Hint**: Think about how antacids work; they neutralize stomach acid.

4. **Use in Fire Extinguishers**:
- Sodium bicarbonate can also be used to produce carbon dioxide in fire extinguishers. When mixed with sulfuric acid (H₂SO₄), it generates CO₂, which helps to smother flames by displacing oxygen.
- The reaction is:
\[ 2\text{NaHCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O} + 2\text{CO}_2 \]

**Hint**: CO₂ is crucial in fire extinguishing because it suffocates the fire.

5. **Use in Baking**:
- In baking, sodium bicarbonate acts as a leavening agent. When it reacts with acidic ingredients (like vinegar or buttermilk), it releases CO₂, which helps dough rise and creates a light texture in baked goods.
- The reaction is similar to that in the previous steps, where CO₂ is produced.

**Hint**: Consider how the texture of bread is affected by gas bubbles.

6. **Conclusion**:
- Based on the above uses, sodium bicarbonate (NaHCO₃) can be used to decrease stomach acidity, prepare CO₂ for fire extinguishers, and help in baking bread. Therefore, the answer to the question is that NaHCO₃ can be used for all of these purposes.

### Final Answer:
Sodium bicarbonate (NaHCO₃) can be used to:
- Decrease acidity of the stomach
- Prepare CO₂ used as a fire extinguisher
- Prepare bread

Thus, the answer is **all of these**.