Which of the following is not a path function ?

Options

A. `DeltaQ`
B. `DeltaQ+DeltaW`
C. `DeltaW`
D. `DeltaQ-DeltaW`

Answer

To solve the question "Which of the following is not a path function?", we need to analyze the options provided in the context of thermodynamics.

### Step-by-step Solution:

1. **Understanding Path Functions and State Functions**:
- Path functions depend on the specific path taken during a process. Examples include heat (ΔQ) and work (ΔW).
- State functions depend only on the initial and final states of a system, regardless of the path taken. An example is internal energy (ΔU).

2. **Identifying the Options**:
- The options provided are:
1. ΔQ
2. ΔQ + ΔW
3. ΔW
4. ΔQ - ΔW

3. **Analyzing Each Option**:
- **Option 1: ΔQ** - Heat is a path function. Therefore, this option is incorrect.
- **Option 2: ΔQ + ΔW** - The sum of two path functions (heat and work) is also a path function. Therefore, this option is incorrect.
- **Option 3: ΔW** - Work is a path function. Therefore, this option is incorrect.
- **Option 4: ΔQ - ΔW** - According to the first law of thermodynamics, we have ΔU = ΔQ - ΔW. Since internal energy (ΔU) is a state function, this expression represents a state function.

4. **Conclusion**:
- Since ΔQ - ΔW represents a state function (internal energy), it is not a path function. Therefore, the correct answer is **Option 4: ΔQ - ΔW**.

### Final Answer:
**Option 4: ΔQ - ΔW is not a path function.**