Which of the following has highest ratio of reducting hydrogen / OH :

Options

A. Orthophosphroric acid
B. Hypophosphorus acid
C. Phosphonic acid
D. Pyrophosphoric acid

Explanation

To solve the problem of determining which oxoacid of phosphorus has the highest ratio of reducing hydrogen to hydroxyl groups (OH), we will analyze each of the given oxoacids step-by-step.

### Step 1: Identify the oxoacids and their formulas
We have four oxoacids of phosphorus:
1. Orthophosphoric acid (H₃PO₄)
2. Hypophosphorus acid (H₃PO₂)
3. Phosphonic acid (H₃PO₃)
4. Pyrophosphoric acid (H₄P₂O₇)

### Step 2: Analyze Orthophosphoric Acid (H₃PO₄)
- **Structure**: H₃PO₄ has three hydroxyl (OH) groups and no reducible hydrogen.
- **Reducing hydrogen count**: 0
- **OH count**: 3
- **Ratio**: 0/3 = 0

### Step 3: Analyze Hypophosphorus Acid (H₃PO₂)
- **Structure**: H₃PO₂ has two hydroxyl (OH) groups and two reducible hydrogens.
- **Reducing hydrogen count**: 2
- **OH count**: 1
- **Ratio**: 2/1 = 2

### Step 4: Analyze Phosphonic Acid (H₃PO₃)
- **Structure**: H₃PO₃ has two hydroxyl (OH) groups and one reducible hydrogen.
- **Reducing hydrogen count**: 1
- **OH count**: 2
- **Ratio**: 1/2 = 0.5

### Step 5: Analyze Pyrophosphoric Acid (H₄P₂O₇)
- **Structure**: H₄P₂O₇ has four hydroxyl (OH) groups and no reducible hydrogen.
- **Reducing hydrogen count**: 0
- **OH count**: 4
- **Ratio**: 0/4 = 0

### Step 6: Compare the ratios
- Orthophosphoric acid: 0
- Hypophosphorus acid: 2
- Phosphonic acid: 0.5
- Pyrophosphoric acid: 0

### Conclusion
The highest ratio of reducing hydrogen to hydroxyl groups is found in **Hypophosphorus acid (H₃PO₂)**, with a ratio of **2**.