Assertion : Metal hydroxides are better antacids than hydrogencarbonates .
Reason : Being insoluble metal hydroxides do not increase the pH above neutrality .

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion .
B. If both assertion and reason are true but reason is not the correct explanation of assertion .
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the assertion-reason question, we will analyze both the assertion and the reason step by step.

### Step 1: Understand the Assertion
**Assertion:** Metal hydroxides are better antacids than hydrogencarbonates.

- **Explanation:** Antacids are substances that neutralize stomach acidity. Metal hydroxides, such as magnesium hydroxide (Mg(OH)₂) and aluminum hydroxide (Al(OH)₃), are commonly used as antacids. They work by neutralizing excess stomach acid (HCl) to relieve heartburn and indigestion.

### Step 2: Understand the Reason
**Reason:** Being insoluble, metal hydroxides do not increase the pH above neutrality.

- **Explanation:** Metal hydroxides are generally insoluble in water, which means they do not dissolve significantly in the stomach. When they react with stomach acid, they neutralize it without significantly increasing the pH of the solution above neutrality (pH 7). This is important because a drastic increase in pH can lead to discomfort and further acid production.

### Step 3: Compare Metal Hydroxides and Hydrogencarbonates
- **Hydrogencarbonates (e.g., Sodium Bicarbonate):** These are soluble in water and can increase the pH of the stomach contents significantly. While they neutralize acid, their solubility can lead to an increase in alkalinity, which may stimulate the stomach to produce more acid in response, potentially leading to a cycle of acid rebound.

### Step 4: Conclusion
- Both the assertion and the reason are correct. Metal hydroxides are indeed better antacids than hydrogencarbonates because their insolubility prevents them from raising the pH above neutrality, thus providing effective relief from acidity without causing further acid production.

### Final Answer
Both the assertion and reason are true, and the reason correctly explains the assertion. Therefore, the answer is option A.

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