What is//are not true abut phosphine `(PH_(3))`?

Options

A. It turns red litmus blue.
B. It reacts with `HCl(aq)`.to give `PH_(4)Cl`.
C. Phosphonium compounds are obtained when anhydrous phosphine reacts with anhydrous halogen acids.
D. It is prepared by hydrolysis of metal phosphides with acids.

Explanation

To determine which statements about phosphine (PH₃) are not true, we will evaluate each statement one by one.

### Step-by-Step Solution:

1. **Evaluate Statement A**: "It turns the red litmus blue."
- Phosphine (PH₃) has a pyramidal structure and contains a lone pair of electrons on phosphorus, which can act as a Lewis base. However, phosphine is a weaker base compared to ammonia (NH₃).
- In its gaseous form, phosphine does not turn red litmus blue. It can only do so in an aqueous solution, which is not specified in the statement. Therefore, this statement is **not true**.

2. **Evaluate Statement B**: "It reacts with HCl to give BH₄Cl."
- When phosphine reacts with hydrochloric acid (HCl), it does not produce BH₄Cl. Instead, it can form phosphonium salts like PH₄Cl, but these salts are unstable and can decompose back into phosphine.
- Thus, this statement is also **not true**.

3. **Evaluate Statement C**: "Phosphonium compounds are obtained when anhydrous phosphine reacts with anhydrous halogen acids."
- This statement is correct. When anhydrous phosphine reacts with anhydrous halogen acids (like HCl or HBr), it does form phosphonium compounds (e.g., PH₄Cl).
- Therefore, this statement is **true**.

4. **Evaluate Statement D**: "It is prepared by hydrolysis of metal phosphide with acids."
- This statement is also correct. For example, sodium phosphide (Na₃P) reacts with sulfuric acid (H₂SO₄) to produce phosphine (PH₃) along with sodium sulfate (Na₂SO₄).
- Hence, this statement is **true**.

### Conclusion:
The statements that are **not true** about phosphine (PH₃) are:
- Statement A: "It turns the red litmus blue."
- Statement B: "It reacts with HCl to give BH₄Cl."