Holme's signals can be given using ____

Explanation

To solve the question "Holme's signals can be given using ____", we will follow these steps:

### Step 1: Understanding Holme's Signals
Holme's signals are used primarily in maritime contexts, particularly in deep seas and oceans, to signal danger to approaching vessels.

**Hint:** Think about the purpose of Holme's signals and where they are typically used.

### Step 2: Identifying the Chemicals Involved
The signals are produced using a specific mixture of chemicals. The two main chemicals involved in generating Holme's signals are calcium phosphide (Ca3P2) and calcium carbide (CaC2).

**Hint:** Consider what chemical reactions might occur when these substances are mixed with water.

### Step 3: Chemical Reactions
When calcium carbide reacts with water, it produces acetylene gas (C2H2) and calcium oxide (CaO):
\[ \text{CaC}_2 + \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_2 + \text{CaO} \]

When calcium phosphide reacts with water, it produces phosphine gas (PH3) and calcium hydroxide (Ca(OH)2):
\[ \text{Ca}_3\text{P}_2 + 6\text{H}_2\text{O} \rightarrow 3\text{Ca(OH)}_2 + 2\text{PH}_3 \]

**Hint:** Look at the products of these reactions and how they relate to signaling.

### Step 4: Signaling Mechanism
The phosphine gas produced is highly flammable and can ignite spontaneously, especially in the presence of diphosphine (P2H4). This combustion produces a luminous flame, which serves as a visual signal to ships in the vicinity.

**Hint:** Think about how the combustion of these gases can serve as a warning signal.

### Step 5: Conclusion
Thus, Holme's signals can be given using a mixture of calcium phosphide and calcium carbide, which when mixed with water, produce flammable gases that create a visible signal.

**Final Answer:** Holme's signals can be given using a mixture of calcium phosphide and calcium carbide.

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