Which of the following is used as an antacid?

Options

A. `MgO`
B. `Mg(OH)_(2)`
C. `MgSO_(4)`
D. `MgCO_(3)`

Explanation

To determine which of the following compounds is used as an antacid, we need to understand the role of antacids and their chemical properties. Antacids are substances that neutralize stomach acidity, which is primarily hydrochloric acid (HCl).

### Step-by-Step Solution:

1. **Understand the Function of Antacids**:
- Antacids are bases that neutralize stomach acid (HCl) to relieve heartburn and indigestion.

2. **Identify Common Antacid Compounds**:
- Common antacids include magnesium hydroxide (Mg(OH)₂), aluminum hydroxide (Al(OH)₃), calcium carbonate (CaCO₃), and sodium bicarbonate (NaHCO₃).

3. **Evaluate the Basicity of Each Compound**:
- Among these, magnesium hydroxide is known for its strong basic character, which makes it effective in neutralizing acids.

4. **Chemical Reaction**:
- The reaction of magnesium hydroxide with hydrochloric acid can be represented as:
\[ Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O \]
- This reaction shows that magnesium hydroxide reacts with hydrochloric acid to form magnesium chloride and water, effectively reducing acidity.

5. **Conclusion**:
- Based on its strong basic properties and effectiveness in neutralizing stomach acid, magnesium hydroxide is commonly used as an antacid.

### Final Answer:
Magnesium hydroxide (Mg(OH)₂) is used as an antacid.

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