Which of the following is true for allotropes of phosphorus?

Options

A. Yellow phosphorus is soluble in `CS_(2)` while red phosphorus is not
B. P-P-P bond angle is `60^(@)` in red phoshprus
C. On heating in air, white phophorus changes to red
D. White phosphorus slowly changes to red phosphorus at ordinar temperature

Answer

To determine which statements are true regarding the allotropes of phosphorus, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the Allotropes of Phosphorus:**
- The main allotropes of phosphorus are **white**, **red**, and **black** phosphorus.

2. **Evaluate Option 1:**
- **Statement:** Yellow phosphorus is soluble in CS2 while red phosphorus is not.
- **Analysis:** Yellow phosphorus (often referred to as white phosphorus) is indeed soluble in carbon disulfide (CS2), while red phosphorus, which has a polymeric structure consisting of chains of P4 tetrahedra linked by covalent bonds, is not soluble in CS2.
- **Conclusion:** This statement is **true**.

3. **Evaluate Option 2:**
- **Statement:** The P-P-P bond angle is 60 degrees in red phosphorus.
- **Analysis:** The bond angle in red phosphorus is actually around **109 degrees**, which corresponds to a tetrahedral arrangement due to its polymeric structure.
- **Conclusion:** This statement is **false**.

4. **Evaluate Option 3:**
- **Statement:** On heating in air, white phosphorus changes to red phosphorus.
- **Analysis:** When white phosphorus is heated in air, it primarily converts to **black phosphorus**, not red phosphorus.
- **Conclusion:** This statement is **false**.

5. **Evaluate Option 4:**
- **Statement:** White phosphorus slowly changes to red phosphorus at ordinary temperature.
- **Analysis:** This is correct; white phosphorus does convert to red phosphorus over time at room temperature.
- **Conclusion:** This statement is **true**.

### Final Conclusion:
- The true statements regarding the allotropes of phosphorus are:
- **Option 1:** Yellow phosphorus is soluble in CS2 while red phosphorus is not.
- **Option 4:** White phosphorus slowly changes to red phosphorus at ordinary temperature.

Thus, the correct answers are **Option 1 and Option 4**.

---