Which among the following is not a state function -

Options

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

Answer

To determine which among the given options is not a state function, we need to understand the definitions of state functions and path functions in thermodynamics.

### Step-by-Step Solution:

1. **Define State Functions**:
State functions are properties that depend only on the state of the system, characterized by its initial and final conditions, regardless of the path taken to get from one state to another. Examples include internal energy (U), enthalpy (H), Gibbs free energy (G), and entropy (S).

2. **Define Path Functions**:
Path functions depend on the specific path taken to achieve a change in state. They are not determined solely by the initial and final states. Examples include work (W) and heat (Q).

3. **Analyze the Options**:
We need to evaluate the four options provided in the question to identify which one is not a state function.

- **Option 1**: Internal Energy (U) - This is a state function.
- **Option 2**: Enthalpy (H) - This is a state function.
- **Option 3**: Work (W) - This is a path function.
- **Option 4**: Gibbs Free Energy (G) - This is a state function.

4. **Identify the Correct Answer**:
From the analysis, we see that Work (W) is the only option that is not a state function. Therefore, the correct answer is **Option 3**.

### Final Answer:
**Option 3: Work (W) is not a state function.**