Which one is known as fusion mixture?

Options

A. `Na_2CO_3` + `NaHCO_3`
B. `Na_2CO_3` + `NaOH`
C. `Na_2CO_3` +`CaSO_4`
D. `Na_2CO_3` + `K_2CO_3`

Answer

To solve the question "Which one is known as fusion mixture?", we will analyze the options provided and identify which combination of substances is typically referred to as a fusion mixture.

### Step-by-Step Solution:

1. **Understanding Fusion Mixture**:
- A fusion mixture is a combination of two or more substances that are heated together to form a homogeneous mixture. In the context of s-block elements, it often refers to a mixture containing salts of sodium and potassium.

2. **Analyzing the Options**:
- **Option A**: Sodium Carbonate (Na2CO3) and Sodium Bicarbonate (NaHCO3)
- This mixture contains only sodium salts and does not include potassium salts.
- **Option B**: Sodium Carbonate (Na2CO3) and Sodium Hydroxide (NaOH)
- Again, this mixture contains only sodium salts.
- **Option C**: Sodium Carbonate (Na2CO3) and Calcium Sulphate (CaSO4)
- This mixture contains sodium and calcium salts, but not potassium.
- **Option D**: Sodium Carbonate (Na2CO3) and Potassium Carbonate (K2CO3)
- This mixture contains both sodium and potassium salts.

3. **Identifying the Correct Answer**:
- Based on the definition of a fusion mixture, the correct option must include both sodium and potassium salts.
- Therefore, **Option D (Sodium Carbonate and Potassium Carbonate)** is the correct answer.

### Final Answer:
The correct answer is **Option D: Sodium Carbonate and Potassium Carbonate**.

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