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It seems that many of the concepts throughout chapter 8 go back to the idea of state functions. I am still having trouble understanding the meaning of a state function as well as its relationship to enthalpy. Can someone please explain how enthalpy is a state function and why one can use the difference between the standard enthalpy of formation of products - reactants to find the standard reaction enthalpy if bond enthalpies are not available?
A state property is a value that is determined by its current state and is not dependent on the path taken to obtain that state. You can determine the change in enthalpy by calculating final - initial. So, you only need the enthalpy of the product and the enthalpy of the reactant to find the enthalpy of a reaction. Think of a mountain and calculating the change in altitude. You only need the final altitude(top of the mountain) - initial altitude(bottom of mountain). (and the curve of the path doesn't matter)
On the other hand, path functions do depend on the path taken from initial to final state. One way to think about state functions is if you had a bank account with $1,000 in it and you took out $100 at once or $25 on four separate occasions, you would have $900 left in your bank account either way and the path taken did not affect this. Enthalpy is a state function and can be thought of mathematically as an integral that depends on the initial and final states but not how it go there.
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