4 posts • Page 1 of 1
Why does Hess's law depend on the fact that enthalpy is a state property?
Hess's law allows you to add two reaction enthalpies together to determine the reaction enthalpy of a third reaction. If enthalpy were not a state function, its value would be dependent on the pathway it took to form the products. This would then invalidate the method of adding two other reaction enthalpies together as this would be a different pathway than the third composite reaction and a different enthalpy value.
Remember that state properties do not depend on a path taken to obtain that state and they can also be added or subtracted. Therefore changes in enthalpy (Hess's Law) are additive like a state function. In addition, enthalpy change at each step of a multi-step reaction can be additive to give the total enthalpy change.
Hess's Law states that the heat of a specific reaction is equal to the sum of the heats of reaction. This depends on the fact that enthalpy is a state function because state function values do not depend on the path that is taken to reach that specific value. Therefore, it is okay to add/subtract these values, as stated in Hess's Law. If enthalpy was not a state function, Hess's Law would be false.
Who is online
Users browsing this forum: No registered users and 1 guest