Question

what is hess law ? explain

Answer 1

Hess's Law

This doesn't just make it easier to write chemical formulas. It also simplifies the process of determining the total enthalpy change. Hess's law states that no matter the multiple steps or intermediates in a reaction the total enthalpy change is equal to the sum of each individual reaction. It is also known as the conservation of energy law. So this means that we can determine the total enthalpy change of A+B+C=ABC by determining this actual reaction's enthalpy change. Or we can determine the enthalpy change for A+B=AB and AB+C=ABC and then add these two together.

Another way to look at this is with a graph. Let's say that it takes a lot of energy for A and B to form AB. But then once it combines with C into ABC it releases a lot of energy:

Answer 2

Definition. Hess's law states that the change of enthalpy in a chemical reaction (i.e. the heat of reaction at constant pressure) is independent of the pathway between the initial and final states



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