Which one of the following is not a state function?

Options

A. Enthalpy
B. Entropy
C. Work
D. Free energy

Explanation

To determine which of the following is not a state function, we first need to understand what a state function is.

### Step-by-Step Solution:

1. **Define State Function**: A state function is a property of a system that depends only on its current state, not on the path taken to reach that state. Examples include internal energy, enthalpy, entropy, and free energy.

2. **Identify Examples of State Functions**:
- **Enthalpy (H)**: Depends only on the initial and final states of the system.
- **Entropy (S)**: Also depends only on the initial and final states.
- **Free Energy (G)**: Similar to enthalpy and entropy, it is a state function.

3. **Identify Non-State Functions**:
- **Work (W)**: The work done can vary depending on the path taken to achieve a particular change in state. For example, the work done to lift an object can differ if it is lifted by stairs versus a lift.

4. **Conclusion**: Since work is dependent on the path taken and not just the initial and final states, it is classified as a path function, not a state function. Therefore, the answer to the question is that work is not a state function.

### Final Answer:
**Work is not a state function.**

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