Which of the following salts exis (s) as decahydrated crystals?

Options

A. Washing soda
B. Glauber's salt
C. Epson salt
D. Grypsum salt

Answer

To determine which of the following salts exist as decahydrated crystals, we need to analyze the molecular formulas of the given salts and identify the number of water molecules associated with each.

### Step-by-Step Solution:

1. **Identify the Salts and Their Formulas:**
- **Washing Soda:** The formula is \( \text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O} \).
- **Glauber's Salt:** The formula is \( \text{Na}_2\text{SO}_4 \cdot 10\text{H}_2\text{O} \).
- **Epsom Salt:** The formula is \( \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \).
- **Gypsum:** The formula is \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \).

2. **Count the Number of Water Molecules:**
- **Washing Soda:** Contains 10 water molecules.
- **Glauber's Salt:** Contains 10 water molecules.
- **Epsom Salt:** Contains 7 water molecules.
- **Gypsum:** Contains 2 water molecules.

3. **Determine Which Salts are Decahydrated:**
- From the analysis, both Washing Soda and Glauber's Salt contain 10 water molecules, qualifying them as decahydrated crystals.
- Epsom Salt and Gypsum do not meet the criteria as they contain fewer water molecules.

4. **Conclusion:**
- The salts that exist as decahydrated crystals are **Washing Soda** and **Glauber's Salt**.

### Final Answer:
The salts that exist as decahydrated crystals are **Washing Soda (Na2CO3·10H2O)** and **Glauber's Salt (Na2SO4·10H2O)**.