Holme's signal uses chemical compound

Options

A. 1. calcium carbide
B. 2. calcium phosphide
C. 3. calcium carbide and calcium phosphide
D. 4. calcium carbide and aluminium carbide.

Explanation

To solve the question regarding the chemical compounds used in Holme's signal, we will follow these steps:

### Step 1: Identify the compounds used in Holme's signal
Holme's signal uses two specific chemical compounds: calcium carbide (CaC2) and calcium phosphide (Ca3P2).

### Step 2: Understand the reaction
When calcium carbide and calcium phosphide react, they produce two gases: phosphine (PH3) and ethyne (C2H2).

### Step 3: Write the chemical reaction
The reaction can be summarized as follows:
\[ \text{CaC}_2 + \text{Ca}_3\text{P}_2 \rightarrow \text{PH}_3 + \text{C}_2\text{H}_2 \]

### Step 4: Explain the purpose of the reaction
The gases produced (phosphine and ethyne) burn together, creating a smoke screen. This smoke is used as a signal, hence the term "Holme's signal."

### Step 5: Conclude with the correct answer
The correct answer to the question is that Holme's signal uses the chemical compounds calcium carbide and calcium phosphide.

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