The following one is example to physical equilibrium

Options

A. `"solid "Leftrightarrow " liquid"`
B. `N_(2)(g)+3H_(2) (g) Leftrightarrow 2NH_(3) (g)`
C. `CaCO_(3) (s) Leftrightarrow CaO(s)+CO_(2)(g)`
D. `2SO_(2) (g)+O_(2) Leftrightarrow 2SO_(3) (g)`

Answer

To determine which example represents physical equilibrium, we need to understand the definitions of physical and chemical equilibrium.

### Step-by-Step Solution:

1. **Understanding Equilibrium Types**:
- There are two main types of equilibrium: physical equilibrium and chemical equilibrium.
- Physical equilibrium occurs when a substance changes from one physical state to another (e.g., solid to liquid) without altering its chemical composition.
- Chemical equilibrium occurs when reactants convert to products through a chemical reaction, and the concentrations of reactants and products remain constant over time.

2. **Analyzing the Options**:
- **Option 1**: A solid changing to a liquid (melting). This is a phase change and represents physical equilibrium.
- **Option 2**: N₂ gas reacting with H₂ gas to form NH₃. This is a chemical reaction and represents chemical equilibrium.
- **Option 3**: CaCO₃ decomposing into CaO and CO₂. This is also a chemical reaction and represents chemical equilibrium.
- **Option 4**: SO₂ gas reacting with O₂ to form SO₃. This is another chemical reaction and represents chemical equilibrium.

3. **Identifying the Correct Answer**:
- Since option 1 describes a phase change (solid to liquid), it is the only example that represents physical equilibrium.
- Therefore, the correct answer to the question is **Option 1**.

### Final Answer:
The following one is an example of physical equilibrium: **Change of solid form into liquid form (Option 1)**.

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