Assertion : In a process, if work = 0 then `DeltaU = q`
Reason : q is difference between initial state and final state of a system.

Answer

To solve the question, we will analyze the assertion and the reason step by step.

### Step 1: Understanding the Assertion
The assertion states: "In a process, if work = 0 then ΔU = q".

According to the first law of thermodynamics, the change in internal energy (ΔU) of a system is given by the equation:
\[ \Delta U = Q + W \]
where:
- ΔU = change in internal energy
- Q = heat added to the system
- W = work done on the system

If work (W) is equal to 0, the equation simplifies to:
\[ \Delta U = Q \]
Thus, the assertion is true.

### Step 2: Understanding the Reason
The reason states: "Q is the difference between initial state and final state of a system."

This statement is misleading. While ΔU is indeed the difference in internal energy between the initial and final states of the system, Q (heat) is not a state function. Heat is the energy transferred due to temperature difference and depends on the path taken during the process, not just the initial and final states. Therefore, the reason is false.

### Step 3: Conclusion
Based on the analysis:
- The assertion is true.
- The reason is false.

### Final Answer
Thus, the correct option is: **Option C: Assertion is true but Reason is false.**

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