All the substance listed below are fertilizers that contribute nitrogen to the soil. Which of these is the richest source of nitrogen on a mass percentage basis ?

Options

A. Urea ,`(NH_(2))_(2) CO`
B. Ammonium nitrate ,`NH_(4)NO_(3)`
C. Nitric oxide , NO
D. Ammonia , `NH_(3)`

Answer

To determine which fertilizer is the richest source of nitrogen on a mass percentage basis, we need to calculate the mass percentage of nitrogen in each compound listed. Here’s how to do it step by step:

### Step 1: Calculate the Molecular Weight of Each Compound

1. **Urea (NH2)2CO**
- Nitrogen (N): 2 atoms × 14 g/mol = 28 g/mol
- Hydrogen (H): 4 atoms × 1 g/mol = 4 g/mol
- Carbon (C): 1 atom × 12 g/mol = 12 g/mol
- Oxygen (O): 1 atom × 16 g/mol = 16 g/mol
- **Total Molecular Weight of Urea** = 28 + 4 + 12 + 16 = 60 g/mol

2. **Ammonium Nitrate (NH4NO3)**
- Nitrogen (N): 2 atoms × 14 g/mol = 28 g/mol
- Hydrogen (H): 4 atoms × 1 g/mol = 4 g/mol
- Oxygen (O): 3 atoms × 16 g/mol = 48 g/mol
- **Total Molecular Weight of Ammonium Nitrate** = 28 + 4 + 48 = 80 g/mol

3. **Nitric Acid (HNO3)**
- Nitrogen (N): 1 atom × 14 g/mol = 14 g/mol
- Hydrogen (H): 1 atom × 1 g/mol = 1 g/mol
- Oxygen (O): 3 atoms × 16 g/mol = 48 g/mol
- **Total Molecular Weight of Nitric Acid** = 14 + 1 + 48 = 63 g/mol

4. **Ammonia (NH3)**
- Nitrogen (N): 1 atom × 14 g/mol = 14 g/mol
- Hydrogen (H): 3 atoms × 1 g/mol = 3 g/mol
- **Total Molecular Weight of Ammonia** = 14 + 3 = 17 g/mol

### Step 2: Calculate the Mass Percentage of Nitrogen in Each Compound

1. **Urea**
- Mass Percentage of Nitrogen = (Weight of Nitrogen / Total Weight) × 100
- = (28 g/mol / 60 g/mol) × 100 = 46.67%

2. **Ammonium Nitrate**
- Mass Percentage of Nitrogen = (28 g/mol / 80 g/mol) × 100 = 35%

3. **Nitric Acid**
- Mass Percentage of Nitrogen = (14 g/mol / 63 g/mol) × 100 = 22.22%

4. **Ammonia**
- Mass Percentage of Nitrogen = (14 g/mol / 17 g/mol) × 100 = 82.35%

### Step 3: Compare the Mass Percentages

- Urea: 46.67%
- Ammonium Nitrate: 35%
- Nitric Acid: 22.22%
- Ammonia: 82.35%

### Conclusion

The richest source of nitrogen on a mass percentage basis is **Ammonia (NH3)** with a mass percentage of **82.35%**.