Quiz One Enthalpy Problem

[Patrick Wilson 2B]

For this problem I was wondering if we just calculate the bonds broken - the bonds formed to find the enthalpy of the reaction. Also I was wondering if the Carbon Oxygen bond breaks before the double bond is formed or if the double bond just forms? Thanks

[Chem_Mod]

For this problem, yes, you are supposed to calculate the enthalpy of bonds broken minus bonds formed. When choosing which bonds are broken, you want to identify any differences between the reactants and the final products, and leave any of the bonds that are the same in both the reactants and products alone. So, looking at bonds broken right now, the organic molecule on the reactant side differs from the products in that there is a C-O single bond instead of a C=O double bond (compared to CO₂), and there is a C-C single bond that is not present on the product side. Looking at bonds formed, we see that comparing the product side to the reactant side, there is a C=O double bond formed in place of the C-O single bond, and a C-H single bond that connects the previously free H+ ion to the second to bottom C.

[Patrick Wilson 2B]

Alright, thank you for the clarification; the most confusing part for me was seeing if the C-O single bond is broken before the double bond is formed. It makes sense now thanks!!