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?
-506 kJ / mol, exothermic
506 kJ / mol, exothermic
-506 kJ / mol, endothermic
506 kJ / mol, endothermic
To calculate the total energy of the reaction, we need to sum up the bond energies of all the bonds broken minus the bond energies of all the bonds formed.
For the bonds broken, we have:
2 H-O bonds broken, so the energy required is 2 * 467 kJ/mol = 934 kJ/mol
For the bonds formed, we have:
2 H-H bonds formed, so the energy released is 2 * -432 kJ/mol = -864 kJ/mol
1 O=O bond formed, so the energy released is -498 kJ/mol
Adding up the energy required to break the bonds and the energy released when forming the bonds:
Energy required = 934 kJ/mol
Energy released = -864 kJ/mol + -498 kJ/mol = -1362 kJ/mol
Total energy of the reaction = Energy required + Energy released = 934 kJ/mol + -1362 kJ/mol = -428 kJ/mol
Since the total energy of the reaction is negative (-428 kJ/mol), the reaction is exothermic.
Therefore, the correct answer is: -506 kJ/mol, exothermic