Question

What is a state function? What are examples of a state function and when it's not a state function?

Answer 1

Hint :We know that the property whose value depends upon path does not come under state function i.e. they are considered as path function or process function. State functions are dependent upon the state of the system i.e. Volume, temperature, pressure, etc. of the system.

Complete Step By Step Answer:
The thermodynamic properties which depend only on initial and final states of the system and not on how the change is brought about are called the state functions. A state function is also referred to as point function. These functions are the functions whose values depend on the state of the substance like temperature, pressure or the amount or type of the substance. In short, state functions do not depend on how the state was reached. Whereas, those properties which depend on the path from two points are known as path functions, also called process functions.
The thermodynamic properties whose values depend only upon the initial and final states of the system are known as state functions. A state function is simply one that depends only on the start and endpoint, and not the path. Example; internal energy $ \left( U \right), $ enthalpy $ \left( H \right), $ entropy $ \left( S \right) $ etc. Gibbs energy is a state function; hence their change depends on the initial and final state of the system.

Note :
Note that the state functions also called as point functions are referred to as the functions which are dependent on the properties of the system only i.e., they are independent of the process which the system undergoes. So, it should be kept in mind which properties are dependent on which functions and it will be easy to decide whether that property is a state function or a path function.