Question

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: 495 kJ/mol
What is the total energy of the reaction? Is this an endothermic or exothermic
reaction?

Answer 1

This problem is providing us with the chemical equation for the decomposition of water to hydrogen and oxygen, the involved bond energies and asks for the total energy of the reaction as well as whether it is endothermic or exothermic. At the end, one comes to the conclusion that  it is exothermic because the total energy is -425 kJ.

Bond energy:

In chemistry, bond energies are defined as the necessary energy to break a bond between two atoms. In this case, we see that water, H2O has two H-O bonds and hydrogen and oxygen have two H-H and one O=O bonds, respectively.

Thus, we write the following heat equation, which comprises the aforementioned bond energies and the stoichiometric coefficients in the reaction:

$\Delta H=2*\Delta H_{H-O}-(2*\Delta H_{H-H}+\Delta H_{O=O})$

Hence, we plug in the given bond energies to obtain:

$\Delta H=2*467kJ/mol-(2*432kJ/mol+495kJ/mol)\\ \\ \Delta H =-425kJ/mol$

Where the negative suggests this is an exothermic reaction as it releases energy (negative enthalpy).

Learn more about bond energies: https://brainly.com/question/26141360