Which of the following is a displacement reaction?

Options

A. `NaOH + HNO_(3) to NaNO_(3) + H_(2)O`
B. `Cu + 2AgNO to Cu(NO_(3))_(2) + 2Ag`
C. `2Hg + O_(2) to 2HgO`
D. `FeC1_(3) + 3NaOH to 3NaC1 + Fe(OH)_(3)`

Explanation

To determine which of the given options is a displacement reaction, we need to analyze each option based on the definition of displacement reactions.

### Step-by-Step Solution:

1. **Understand Displacement Reactions**:
- A displacement reaction occurs when one element or ion displaces another in a compound. This can happen with either positive ions (cations) or negative ions (anions), but not both simultaneously in a single displacement reaction.

2. **Analyze the Options**:
- We need to evaluate each option provided to see if it fits the criteria for a displacement reaction.

3. **Option 1**:
- Reaction: Na⁺ + H⁺ → H₂O + NO₃⁻ + OH⁻
- Analysis: In this reaction, both a positive ion (Na⁺) and a negative ion (OH⁻) are being replaced. This indicates a double displacement reaction, not a single displacement reaction.
- Conclusion: **Not a displacement reaction**.

4. **Option 2**:
- Reaction: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
- Analysis: Here, copper (Cu) is neutral and is displacing the silver ion (Ag⁺) from silver nitrate (AgNO₃). Only the positive ion (Ag⁺) is being displaced, which fits the criteria for a displacement reaction.
- Conclusion: **This is a displacement reaction**.

5. **Option 3**:
- Reaction: Hg + O₂ → HgO
- Analysis: This reaction involves the combination of mercury (Hg) and oxygen (O₂) to form mercury oxide (HgO). This is a combination reaction, not a displacement reaction.
- Conclusion: **Not a displacement reaction**.

6. **Option 4**:
- Reaction: Fe³⁺ + NaCl → Na⁺ + FeCl₃
- Analysis: In this reaction, Fe³⁺ is replacing Na⁺ in the compound NaCl. This indicates that both ions are being exchanged, which is characteristic of a double displacement reaction.
- Conclusion: **Not a displacement reaction**.

### Final Answer:
The correct option that represents a displacement reaction is **Option 2**: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag.

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