Orthoboric acid on strong heating gives `"………….."`.

Answer

To solve the question "Orthoboric acid on strong heating gives '…………..'", we will follow these steps:

### Step 1: Identify Orthoboric Acid
Orthoboric acid is represented by the chemical formula H₃BO₃.

### Step 2: Heating Orthoboric Acid
When orthoboric acid is subjected to strong heating, it undergoes a series of reactions. The first reaction occurs when it is heated to about 373 K (100 °C), leading to the formation of metaboric acid (HBO₂) and the release of water (H₂O).

**Reaction:**
\[ \text{H}_3\text{BO}_3 \xrightarrow{heat} \text{HBO}_2 + \text{H}_2\text{O} \]

### Step 3: Further Heating of Metaboric Acid
If metaboric acid (HBO₂) is heated further, it can dehydrate to form boron trioxide (B₂O₃) and water.

**Reaction:**
\[ 2 \text{HBO}_2 \xrightarrow{heat} \text{B}_2\text{O}_3 + \text{H}_2\text{O} \]

### Step 4: Final Product from Strong Heating
Upon strong heating of orthoboric acid, the final product formed is boron trioxide (B₂O₃).

**Final Reaction:**
\[ \text{H}_3\text{BO}_3 \xrightarrow{strong\ heat} \text{B}_2\text{O}_3 + \text{H}_2\text{O} \]

### Conclusion
Thus, the answer to the question is:
**Orthoboric acid on strong heating gives Boron trioxide (B₂O₃).**

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