Concept:A state function is a thermodynamic property whose value depends strictly on the current state of the system (e.g., its temperature, pressure, and volume) and is entirely independent of the path or history used to reach that state.
Formula:$$ \Delta U = q + w $$
Solution:- Enthalpy (H), Internal energy (U or E), and Pressure (P) are all state functions; their changes (\( \Delta H, \Delta U, \Delta P \)) only depend on final minus initial states.
- Work (w) and Heat (q) are "path functions". The amount of work done or heat transferred depends entirely on how the process was carried out (e.g., reversible vs irreversible expansion).
- Therefore, Work is not a state function.
Why other options are incorrect:Pressure, Internal energy, and Enthalpy all have fixed values at a specific thermodynamic state regardless of the system's history.
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