Which of the following bases cannot be used as antacids?
A. Sodium carbonate
B. Sodium hydrogencarbonate
C. Magnesium hydroxide
D. Sodium hydroxide

Options

A. A and B
B. B and C
C. A and D
D. B and D

Answer

To determine which of the following bases cannot be used as antacids, we first need to understand what antacids are and their purpose.

### Step 1: Define Antacids
Antacids are substances that neutralize stomach acidity. They are commonly used to relieve symptoms such as heartburn, indigestion, and upset stomach.

### Step 2: Identify Common Antacids
Some commonly used antacids include:
- Sodium hydrogen carbonate (baking soda)
- Magnesium hydroxide

### Step 3: Analyze Each Option
Now, let’s analyze the given options:

- **A. Sodium carbonate**: This is also known as washing soda and is highly alkaline. It can cause irritation or burns if ingested, so it is not suitable as an antacid.

- **B. Sodium hydrogencarbonate**: This is a mild base and is commonly used as an antacid. It effectively neutralizes stomach acid without causing harm.

- **C. Magnesium hydroxide**: This is another common antacid that neutralizes stomach acid and is safe for consumption.

- **D. Sodium hydroxide**: This is a strong base and can be very caustic. It can cause burns and is not safe to use as an antacid.

### Step 4: Conclusion
From the analysis:
- Sodium carbonate (A) and Sodium hydroxide (D) cannot be used as antacids due to their highly alkaline nature and potential to cause harm.

### Final Answer
The bases that cannot be used as antacids are:
- **A. Sodium carbonate**
- **D. Sodium hydroxide**

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