`underset(("Hydrated salt"))((A)) underset("heated")overset("Storngly")tounderset("glassy bead")underset("transparent")ubrace(B+C)`
`H_(3)BO_(3) underset("heated")overset("Strongly")toC+D`
Find the number of water of crystallizations in (A) :-

Options

A. 4
B. 5
C. 10
D. 24

Answer

To solve the problem, we need to analyze the two reactions provided and determine the number of water molecules of crystallization in the hydrated salt (A).

### Step-by-Step Solution:

1. **Identify the Compounds in the Second Reaction**:
The second reaction involves heating boric acid (H₃BO₃). Upon strong heating, it produces two compounds, which we will denote as C and D.

- **Reaction**:
\[ H_3BO_3 \xrightarrow{\text{strongly heated}} C + D \]

2. **Determine the Products of the Second Reaction**:
When boric acid (H₃BO₃) is heated, it decomposes to form metaboric acid (HBO₂) and water (H₂O). The balanced equation is:
\[ 2 H_3BO_3 \xrightarrow{\text{strongly heated}} HBO_2 + H_2O \]
Further heating of metaboric acid (HBO₂) leads to the formation of boric anhydride (B₂O₃) and more water. The balanced equation for this step is:
\[ 2 HBO_2 \xrightarrow{\text{strongly heated}} B_2O_3 + H_2O \]
Thus, we find that:
- **C = B₂O₃ (boric anhydride)**
- **D = H₂O (water)**

3. **Identify the Compounds in the First Reaction**:
The first reaction involves a hydrated salt (A) that, when heated strongly, produces two compounds (B and C). We know from the previous step that C is B₂O₃.

- **Reaction**:
\[ A \xrightarrow{\text{strongly heated}} B + C \]

4. **Determine the Hydrated Salt (A)**:
The hydrated salt (A) is likely sodium tetraborate decahydrate, which has the formula Na₂B₄O₇·10H₂O. When this compound is heated, it produces sodium metaborate (NaBO₂) and boric anhydride (B₂O₃).

- **Balanced Equation**:
\[ Na_2B_4O_7 \cdot 10H_2O \xrightarrow{\text{strongly heated}} 2 NaBO_2 + B_2O_3 + 10 H_2O \]
Here, we can see that the number of water molecules of crystallization in (A) is 10.

5. **Conclusion**:
The number of water of crystallization in the hydrated salt (A) is **10**.

### Final Answer:
The number of water of crystallization in (A) is **10**.

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