Which of the following is not a physical equilibrium ?

Options

A. `Ice rarr Water`
B. `I_(2)(s) rarr I_(2)(g)`
C. `S(l) rarr S(g)`
D. `3O_(2)(g) rarr 2O_(3)(g)`

Explanation

To determine which of the following is not a physical equilibrium, we first need to understand what constitutes a physical equilibrium.

### Step-by-Step Solution:

1. **Definition of Physical Equilibrium**:
Physical equilibrium occurs when substances change between different physical states (solid, liquid, gas) without changing their chemical composition. This means that the equilibrium involves transitions such as solid ↔ liquid, liquid ↔ gas, or solid ↔ gas.

2. **Identifying Physical Equilibrium Examples**:
- **Solid ↔ Liquid**: This is a physical equilibrium, as seen in the melting of ice to water.
- **Liquid ↔ Gas**: This is also a physical equilibrium, such as water evaporating to form steam.
- **Solid ↔ Gas**: This is another example of physical equilibrium, like the sublimation of dry ice (solid CO2) to carbon dioxide gas.

3. **Analyzing the Options**:
- If we have options like:
- A: Ice and Water (Solid and Liquid)
- B: Solid and Gas (e.g., Dry Ice and CO2)
- C: Water and Steam (Liquid and Gas)
- D: O2 and O3 (Both are Gases)
- We need to check if the substances in each option are in different phases.

4. **Identifying the Non-Physical Equilibrium**:
- In option D, both O2 (oxygen gas) and O3 (ozone gas) are in the same phase (gas). Therefore, this does not represent a physical equilibrium since there is no change in phase.

5. **Conclusion**:
Based on the analysis, the option that is not a physical equilibrium is D: O2 and O3.

### Final Answer:
**D: O2 and O3 is not a physical equilibrium.**

---