I attempted this problem in a quiz and got it wrong. I am confused as to how to properly assign positive and negative values for energy, and how to land at the answer.
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You add  all ond energys of the educts and all of the products and built ΔH of educts - products.

1x C-C + 6 x C-H + 1 Cl-Cl -(1x C-C + 5 x C-H + 1 x H-Cl)

Solution c = - 102 kJ/mol

Quote from: ann on October 16, 2022, 08:17:04 PM
I attempted this problem in a quiz and got it wrong. I am confused as to how to properly assign positive and negative values for energy, and how to land at the answer.

First you draw Lewis dot diagrams of all reactants and products
Now check all bonds of the reactants which are broken and all bonds of the products which are formed.
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Bond breaking is endothermic and bond making is exothermic.
Delta H (reaction) = Sum of all bond enthalpies of the reactants - sum of all bond enthalpies of the products.