`Ca_(3)P_(2)+H_(2)O to Ca(OH)_(2)+(A)`
Product (A) is used in

Options

A. Holme's signal
B. Smoke screen
C. Manufacture of `NH_(4)NO_(3)`
D. Both 1 and 2

Answer

To solve the problem, we need to analyze the reaction between calcium phosphide (Ca₃P₂) and water (H₂O) and identify the product (A) formed in the reaction. Here’s a step-by-step breakdown of the solution:

### Step 1: Write the reaction equation
The reaction given is:
\[ \text{Ca}_3\text{P}_2 + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{A} \]

### Step 2: Identify the products
When calcium phosphide reacts with water, it produces calcium hydroxide and phosphine gas (PH₃). Therefore, the balanced equation can be written as:
\[ \text{Ca}_3\text{P}_2 + 6 \text{H}_2\text{O} \rightarrow 3 \text{Ca(OH)}_2 + 2 \text{PH}_3 \]

Here, product (A) is phosphine (PH₃).

### Step 3: Analyze the properties of phosphine
Phosphine is a colorless gas with a characteristic odor resembling that of rotten fish. It is highly toxic and has various applications.

### Step 4: Identify the uses of phosphine
Phosphine is used in:
1. **Pallm signal**: It is used in signaling devices, particularly in maritime contexts, where it can be released into the air to create a visible signal.
2. **Smoke screens**: Phosphine can also be utilized to create dense smoke screens for military or safety purposes.

### Step 5: Conclusion
Thus, product (A) is phosphine (PH₃), which is used in both signaling and smoke screen applications.

### Final Answer
Product (A) is phosphine (PH₃), which is used in both signaling and smoke screens.

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