Question

Which one of the following does not have water of crystallization?

• A. Blue vitriol
• B. Baking soda
• C. Washing soda
• D. Gypsum

Hint:

Water of crystallization is represented in chemical formulas by a dot followed by a specific number of \(H_2O\) molecules (e.g., \(\cdot nH_2O\)).
Baking soda (\(NaHCO_3\)) is written without any such water attachment, meaning it is anhydrous.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify which of the given chemical compounds does not contain water of crystallization in its solid crystal structure.

Step 2: Key Formula or Approach:
Water of crystallization is the fixed number of water molecules chemically bonded in a definite proportion within a single formula unit of a salt's crystalline structure.

Step 3: Detailed Explanation:

• Let us examine the chemical formulas of each option:
- (A) Blue vitriol: Hydrated copper sulfate. Its chemical formula is:
\[ CuSO_4 \cdot 5H_2O \] It contains 5 water molecules of crystallization, which give it its characteristic blue color.
- (B) Baking soda: Sodium bicarbonate. Its chemical formula is:
\[ NaHCO_3 \] Baking soda exists as an anhydrous white crystalline powder and does not contain any water of crystallization.
- (C) Washing soda: Sodium carbonate decahydrate. Its chemical formula is:
\[ Na_2CO_3 \cdot 10H_2O \] It contains 10 water molecules of crystallization.
- (D) Gypsum: Hydrated calcium sulfate. Its chemical formula is:
\[ CaSO_4 \cdot 2H_2O \] It contains 2 water molecules of crystallization.

• Therefore, baking soda is the only compound in the list that does not contain water of crystallization.


Step 4: Final Answer:
Baking soda does not have water of crystallization.