Which of the following salts does not contain water of crystallization?

Options

A. Copper sulphate
B. Gypsum
C. Washing soda
D. Baking soda

Explanation

To determine which of the following salts does not contain water of crystallization, we need to analyze the chemical formulas of the given salts. Here’s a step-by-step solution:

### Step 1: Understand Water of Crystallization
Water of crystallization refers to the water molecules that are incorporated into the crystal structure of a salt. These water molecules are essential for the stability and formation of the crystalline structure.

### Step 2: Identify the Salts
We will look at the chemical formulas of the salts mentioned in the question:

1. **Copper Sulfate**: CuSO4·5H2O
2. **Gypsum**: CaSO4·2H2O
3. **Washing Soda**: Na2CO3·10H2O
4. **Baking Soda**: NaHCO3

### Step 3: Analyze Each Salt
- **Copper Sulfate (CuSO4·5H2O)**: Contains 5 water molecules, so it has water of crystallization.
- **Gypsum (CaSO4·2H2O)**: Contains 2 water molecules, so it has water of crystallization.
- **Washing Soda (Na2CO3·10H2O)**: Contains 10 water molecules, so it has water of crystallization.
- **Baking Soda (NaHCO3)**: Does not contain any water molecules in its formula, indicating it is an anhydrous salt.

### Step 4: Conclusion
From the analysis, we can conclude that **Baking Soda (NaHCO3)** does not contain water of crystallization.

### Final Answer
The salt that does not contain water of crystallization is **Baking Soda (NaHCO3)**.

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