Orthophosphorus acid on heating gives ______

Options

A. Hypophosphorus acid
B. Orthophosphoric acid
C. Phosphene gas
D. Both (2) & (3)

Answer

To solve the question "Orthophosphorus acid on heating gives ______", we can follow these steps:

### Step 1: Identify Orthophosphorus Acid
Orthophosphorus acid is represented by the chemical formula H₃PO₃.

### Step 2: Understand the Reaction Upon Heating
When orthophosphorus acid (H₃PO₃) is heated, it undergoes a decomposition reaction.

### Step 3: Products of the Decomposition
The decomposition of orthophosphorus acid upon heating produces:
1. Orthophosphoric acid (H₃PO₄)
2. Phosphine gas (PH₃)

### Step 4: Write the Balanced Equation
The balanced equation for the reaction can be represented as:
\[ 2 H₃PO₃ \rightarrow H₃PO₄ + PH₃ \]

### Step 5: Conclusion
From the reaction, we conclude that heating orthophosphorus acid yields both orthophosphoric acid and phosphine gas. Therefore, the correct answer is:
**Orthophosphoric acid and phosphine gas.**

### Final Answer
Orthophosphorus acid on heating gives **both B (orthophosphoric acid) and C (phosphine gas)**.