3 Methods

[Jasmine 2C]

Can someone explain how and when the three methods should be the used?

[cassidysong 1K]

The three methods are Hess's Law, using bond enthalpies, and delta H = Σ delta Hf of products - Σ delta Hf of reactants.
Using the bond enthalpy method is the least accurate so if you can use other methods that's preferred.

[Nikki Razal 1L]

1) Hess's Law: use when you know delta H, use addition/subtraction to add up total enthalpy changes
2) using bonding enthalpies to calculate deltaH: add together energy required for the bonds in the reactants to break (positive values) and the energy released when bonds break (the energy of the products as negative values)
3) standard reaction enthalpies: calculate deltaH= sum of deltaHproducts- sum of deltaHreactants

[Kristina Rizo 2K]

The three methods are Hess's Law, using bond enthalpies, and delta H = Σ delta Hf of products - Σ delta Hf of reactants.
Using the bond enthalpy method is the least accurate so if you can use other methods that's preferred.

This was extremely helpful thanks! But do you know which is more accurate (Hess’s law or delta Hf products- delta Hf reactants)?