Which of the following statement is true ?

Options

A. Ammonia is the weakest reducing agent and the strongest base among Group 15 hydrides
B. Ammonia is the strongest reducing agent as well as the weakest base among Group 15 hydrides
C. Ammonia is the weakest reducing agent as well as the strongest base among Group 15 hydrides
D. Ammonia is the strongest reducing agent and the weakest base among Group 15 hydrides

Answer

To determine which statement is true regarding ammonia and its properties among group 15 hydrides, we will analyze the statements step by step.

### Step 1: Identify Group 15 Hydrides
Group 15 hydrides include:
- NH3 (Ammonia)
- PH3 (Phosphine)
- AsH3 (Arsine)
- SbH3 (Stibine)
- BiH3 (Bismuthine)

### Step 2: Analyze Reducing Agent Strength
A reducing agent is a substance that donates electrons or reduces another substance. The strength of a reducing agent can be related to the thermal stability of the hydride. As we move down the group from nitrogen to bismuth, the bond strength between the central atom and hydrogen decreases due to increasing atomic size and bond length.

- **Conclusion**: NH3 (Ammonia) is the weakest reducing agent because it has the strongest bond with hydrogen compared to the other hydrides. Conversely, BiH3 (Bismuthine) is the strongest reducing agent because it has the weakest bond with hydrogen.

### Step 3: Analyze Basicity
A base is a substance that can donate a lone pair of electrons. In the case of ammonia, it has a lone pair of electrons on the nitrogen atom. As we move down the group, the size of the central atom increases, which causes the lone pair to be more diffuse and less available for donation.

- **Conclusion**: NH3 is the strongest base among the group 15 hydrides because its lone pair is concentrated in a smaller volume, making it more available for donation.

### Step 4: Evaluate the Statements
Now we evaluate the statements provided:

1. **Statement 1**: "Ammonia is the weakest reducing agent and strongest base among group 15 hydrides."
- This statement is **true**.

2. **Statement 2**: "Ammonia is the strongest reducing agent."
- This statement is **false**.

3. **Statement 3**: "Ammonia is the weakest base."
- This statement is **false**.

### Final Conclusion
The only true statement is:
- **Ammonia is the weakest reducing agent and strongest base among group 15 hydrides.**