Hess' Law

[Sahir Eusuff 2H]

What is the significance of Hess' Law?

[Neelaj Das 3I]

This is an important concept that will help you find the enthalpy of a given reactions based on the sum of reactions leading up to it. Knowing Hess's Law will allow you to easily find the enthalpy of a net reaction by adding up the enthalpies of the reactions added together to form that main reaction.

[Crystal Ros 2L]

Hess’s Law states that the enthalpy change of an overall reaction is the summation of each individual reaction’s enthalpy change. This is because enthalpy is a state property so we can add or subtract if the values are derived from the same phase.

[Devon Shao 1E]

To expand upon other answers here, Hess's Law is practically applied in the methods of finding enthalpy changes that Dr. Lavelle went over in his lecture.

Because Hess's Law states that it is additive, you can add the enthalpy change at each step of a multi-step reaction into the total enthalpy change of the reaction. Thus, given the enthalpy of two reactions, if they add up to a third reaction you can also find the enthalpy of the third reaction. There are many more complicated ways the additive properties can be applied; this is just how it was used in Method 1 in the lecture.

[tim_villasenor 1k]

important to remember how enthalpy is a state function. This is important because Hess' law demonstrates how when you add two enthalpies you just add the values. This is different than equilibrium values where you multiply them.

[Bela Patel 2B]

Hess' law is significant in that it can be used to determine if the energy change in an overall chemical reaction is equal to the sum of the energy changes in the individual reactions within it.