The formula of soda ash is

Options

A. `Na_(2)CO_(3)*10H_(2)O`
B. `Na_(2)CO_(3)*2H_(2)O`
C. `Na_(2)CO_(3)*H_(2)O`
D. `Na_(2)CO_(3)`

Answer

To determine the formula of soda ash, we need to identify what soda ash is chemically. Soda ash is commonly known as sodium carbonate.

### Step-by-Step Solution:

1. **Understanding Soda Ash**:
- Soda ash is a term used to refer to sodium carbonate (Na2CO3). It is a white, odorless powder that is soluble in water.

2. **Identifying the Options**:
- The options provided are:
- A) Sodium carbonate with 10 H2O (Na2CO3·10H2O)
- B) Sodium carbonate with 2 H2O (Na2CO3·2H2O)
- C) Sodium carbonate with 1 H2O (Na2CO3·H2O)
- D) Anhydrous sodium carbonate (Na2CO3)

3. **Analyzing Each Option**:
- Option A refers to sodium carbonate decahydrate (washing soda), which is not soda ash.
- Option B refers to sodium carbonate dihydrate, which is also not soda ash.
- Option C refers to sodium carbonate monohydrate, which is not soda ash.
- Option D refers to anhydrous sodium carbonate, which is indeed soda ash.

4. **Conclusion**:
- The correct formula for soda ash is the anhydrous form of sodium carbonate, which is Na2CO3. Therefore, the correct answer is option D.

### Final Answer:
The formula of soda ash is **Na2CO3** (anhydrous sodium carbonate).