Which is not state function ?

Options

A. Heat at constant volume
B. Work in adiabatic process
C. Heat at constant pressure
D. Work in isobaric process

Explanation

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

### Step-by-step Solution:

1. **Understanding State Functions**:
- State functions are properties that depend only on the state of the system, not on how it reached that state. Examples include internal energy (U), enthalpy (H), and pressure (P).

2. **Analyzing Each Option**:
- **Option A: Heat at Constant Volume (Q_v)**:
- At constant volume, the heat added to the system can be expressed as the change in internal energy (ΔU). Since internal energy is a state function, heat at constant volume is also a state function.

- **Option B: Work in Adiabatic Process (W)**:
- In an adiabatic process, there is no heat exchange (Q = 0). According to the first law of thermodynamics, ΔU = Q + W, which simplifies to W = ΔU. Since ΔU is a state function, work done in an adiabatic process is also a state function.

- **Option C: Heat at Constant Pressure (Q_p)**:
- Heat at constant pressure can be expressed as the change in enthalpy (ΔH). Enthalpy is a state function, so heat at constant pressure is also a state function.

- **Option D: Work in Isobaric Process (W)**:
- Work done in an isobaric process can be expressed as W = -PΔV. This expression depends on the path taken (the change in volume), making work in an isobaric process a path function.

3. **Conclusion**:
- Based on the analysis, the correct answer is **Option D: Work in Isobaric Process** is not a state function; it is a path function.

### Final Answer:
**Option D: Work in Isobaric Process is not a state function.**