Which of the following is not a general characteristic of equilibrium involving physical processes ?

Options

A. (a) Equilibrium is possible only in a closed system at a given temperature.
B. (b) The equilibrium is dynamic in nature.
C. (c) Measurable properties of the system keep changing.
D. (d) Equilibrium can be attained from both sides of the reaction.

Explanation

To solve the question "Which of the following is not a general characteristic of equilibrium involving physical processes?", we will analyze each option provided and determine which one does not align with the characteristics of physical equilibrium.

### Step-by-Step Solution:

1. **Understanding Physical Equilibrium**:
- Physical equilibrium refers to the state where two physical processes (like solid-liquid, liquid-gas, or gas-solid) occur at equal rates, resulting in no net change in the system.

2. **Analyzing the Options**:
- **Option A**: "Equilibrium is possible only in a closed system at a given temperature."
- This statement is **correct**. In a closed system, the substances involved do not escape, allowing equilibrium to be established.

- **Option B**: "The equilibrium is dynamic in nature."
- This statement is also **correct**. At equilibrium, the processes continue to occur, but the rates of the forward and reverse reactions are equal, making it dynamic.

- **Option C**: "Measurable properties of the system keep changing."
- This statement is **incorrect**. At equilibrium, measurable properties (like concentration, pressure, and temperature) remain constant, not changing.

- **Option D**: "Equilibrium can be attained from both sides of the reaction."
- This statement is **correct**. Equilibrium can be reached regardless of whether the system starts from the reactants or products.

3. **Conclusion**:
- The option that is not a general characteristic of equilibrium involving physical processes is **Option C**: "Measurable properties of the system keep changing."

### Final Answer:
The answer is **Option C**.

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