The question is about identifying a thermodynamic state function, which is a key concept in chemistry, especially in the study of thermodynamics.
Definition of a State Function: A state function is a property of a system that depends only on the current state of the system, not on the way the system got to that state. This means its value is independent of the path taken to reach that state. Examples of state functions include internal energy, enthalpy, entropy, and the Gibbs free energy.
Now, let us analyze the given options:
- Option 1: "used to determine heat changes"
This is incorrect. Heat is a path function, not a state function. The heat change depends on the path taken because it is related to the exchange of energy due to temperature differences.
- Option 2: "whose value is independent of path"
This is correct. As explained, state functions are path-independent, meaning their values depend solely on the state of the system.
- Option 3: "used to determine pressure volume work"
This is incorrect. Pressure-volume work is again a path function because it varies with the path taken by the process, defined as W = \int P \, dV.
- Option 4: "whose value depends on temperature only"
This is incorrect. State functions may depend on various state variables, not just temperature. For example, enthalpy and internal energy depend on both temperature and pressure/volume.
Conclusion: The most suitable answer is Option 2: "whose value is independent of path".