Which one is a state function :-

Options

A. Heat supplied at constant pressure
B. Heat supplied at constant volume
C. Enthalpy
D. All of the above

Answer

To determine which of the given options is a state function, we first need to understand what a state function is.

### Step-by-step Solution:

1. **Definition of State Function**:
A state function is a property of a system that depends only on the current state of the system, not on the path taken to reach that state. It is defined by the initial and final conditions of the system.

2. **Analyzing the Options**:
We have three options to analyze:
- Heat supplied at constant pressure
- Heat supplied at constant volume
- Enthalpy

3. **Heat Supplied at Constant Pressure**:
- The heat supplied at constant pressure is represented as \( Q_p \), which is equal to the change in enthalpy (\( \Delta H \)).
- Since enthalpy depends only on the initial and final states of the system, \( Q_p \) is a state function.

4. **Heat Supplied at Constant Volume**:
- The heat supplied at constant volume is represented as \( Q_v \), which is equal to the change in internal energy (\( \Delta U \)).
- Similar to enthalpy, internal energy also depends only on the initial and final states, making \( Q_v \) a state function.

5. **Enthalpy**:
- Enthalpy (\( H \)) itself is a state function as it is defined based on the state of the system (pressure, temperature, and composition).
- Therefore, it is also a state function.

6. **Conclusion**:
- Since all three options (heat supplied at constant pressure, heat supplied at constant volume, and enthalpy) are state functions, the correct answer is "all of the above".

### Final Answer:
The answer is **all of the above** (option 4).

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