Which is the correct statement for the given acids ?

Options

A. Phosphinic acid is a diprotic acid while phosphonic acid is a monoprotic acid
B. Phosphinic acid is a monoprotic acid while phosphoric acid is a diprotic acid
C. Both are diprotic acids
D. Both are triprotic acids

Answer

To determine the correct statement regarding phosphonic acid and phosphoric acid, we need to analyze their structures and the number of replaceable hydrogen ions (protons) they possess.

### Step-by-Step Solution:

1. **Identify the Acids**:
- We have two acids to consider: phosphonic acid and phosphoric acid.

2. **Draw the Structures**:
- **Phosphonic Acid (H₃PO₃)**:
- The structure of phosphonic acid can be represented as follows:
```
O
||
H - P - OH
|
H
```
- In this structure, there are three hydrogen atoms, but only one of them is replaceable (the one attached to the hydroxyl group).

- **Phosphoric Acid (H₃PO₄)**:
- The structure of phosphoric acid is:
```
O
||
OH - P - O - H
|
OH
```
- Phosphoric acid has three hydroxyl groups, and thus it can release three protons.

3. **Determine the Type of Acid**:
- **Phosphonic Acid**: Since it has only one replaceable hydrogen ion, it is classified as a **monoprotic acid**.
- **Phosphoric Acid**: It has three replaceable hydrogen ions, making it a **triprotic acid**.

4. **Evaluate the Options**:
- Option 1: "Phosphonic acid is a diprotic acid while phosphonic acid is a monoprotic acid." - Incorrect.
- Option 2: "Phosphonic acid is a monoprotic acid while phosphoric acid is a diprotic acid." - Incorrect (phosphoric acid is triprotic).
- Option 3: "Both are diprotic acids." - Incorrect.
- Option 4: "Both are triprotic acids." - Incorrect.
- Option 5: "Phosphonic acid is monoprotic and phosphoric acid is triprotic." - Correct.

5. **Conclusion**:
- The correct statement is that **phosphonic acid is a monoprotic acid, and phosphoric acid is a triprotic acid**.

### Final Answer:
The correct statement is: **Phosphonic acid is a monoprotic acid and phosphoric acid is a triprotic acid.**