Use the reaction equation and bond energies to answer the question. 2H2O → 2H2 + O2 H-O: 467 kJ/mol H-H: 432 kJ/mol O=O: 498 kJ/mol What is the total energy of the reaction? Is this an endothermic or exothermic reaction
To find the total energy of the reaction using bond energies, we need to calculate the total energy required to break the bonds in the reactants and compare that to the total energy released when the new bonds form in the products.
Reactants:
- 2 H-O bonds x 467 kJ/mol = 934 kJ/mol
- 4 H-H bonds x 432 kJ/mol = 1728 kJ/mol
- Total energy required to break bonds in reactants: 2662 kJ/mol
Products:
- 2 H-H bonds x 432 kJ/mol = 864 kJ/mol
- 1 O=O bond x 498 kJ/mol = 498 kJ/mol
- Total energy released when new bonds form in products: 1362 kJ/mol
Total energy change = energy required - energy released
= 2662 kJ/mol - 1362 kJ/mol
= 1300 kJ/mol
Since the total energy change is positive (1300 kJ/mol), this is an endothermic reaction.