Question

So, I have been studying thermodynamics, in it I read that state functions are those functions which depend only on one state of the system and are independent of the path taken, which is pretty easy to understand. And this clears why properties like enthalpy, pressure, volume etc are state functions. Then there was the statement,

Change in a state function is not a state function.

which took me some time to understand, but I got it once I referred to the original definition of a state function. But now when I read about Hess law, which basically states that change in a state function is independent of the path taken, I'm confused as doesn't this imply that change in state function is infact a state function. Can someone please clarify this.

Answer 1

In thermodynamics, state functions are properties of a system that depend only on its present state and are independent of the path taken. The change in a state function is not a state function, but it follows the same principles as other state functions in terms of being independent of the path taken.

Step-by-step explanation:

In thermodynamics, a state function is a property of a system that depends only on its present state and is independent of the path taken to reach that state. Examples of state functions include temperature, pressure, volume, and potential energy. On the other hand, heat and work are not state functions because they are path dependent. However, the change in a state function is also a state function, as stated by Hess's law.

Hess's law states that the change in a state function, such as enthalpy, is independent of the path taken. This means that you can calculate the change in enthalpy of a reaction by adding together the changes in enthalpy for individual steps, even if the overall reaction does not occur via those steps. So, while the change in a state function is not a state function itself, it follows the same principles as other state functions in terms of being independent of the path taken.