Question

Use the reaction equation and bond energies to answer the question.2H2O → 2H2 + O2H-O: 467 kJ/molH-H: 432 kJ/molO=O: 498 kJ/molWhat is the total energy of the reaction? Is this an endothermic or exothermic reaction?(1 point)Responses–506 kJ/mol, endothermic–506 kJ/mol, endothermic506 kJ/mol, endothermic506 kJ/mol, endothermic–506 kJ/mol, exothermic–506 kJ/mol, exothermic506 kJ/mol, exothermic

Answer 1

To determine the total energy change for the reaction \( 2H_2O \rightarrow 2H_2 + O_2 \), we can use the bond energies provided for each type of bond involved.

1. **Break the bonds in the reactants**:
- In 2 \( H_2O \), there are 4 O-H bonds (2 per water molecule).
- Therefore, the energy required to break the O-H bonds is:
\[
4 \times 467 \, \text{kJ/mol} = 1868 \, \text{kJ/mol}
\]

2. **Form the bonds in the products**:
- In the products, we have 2 \( H_2 \) molecules (which has 2 H-H bonds) and one \( O_2 \) molecule (which has 1 O=O bond).
- The energy released when forming the bonds is:
\[
(2 \times 432 \, \text{kJ/mol}) + (1 \times 498 \, \text{kJ/mol}) = 864 \, \text{kJ/mol} + 498 \, \text{kJ/mol} = 1362 \, \text{kJ/mol}
\]

3. **Calculate the total energy of the reaction**:
- The overall change in energy (ΔE) for the reaction is the energy required to break the bonds minus the energy released when forming the bonds:
\[
\Delta E = \text{Energy to break bonds} - \text{Energy to form bonds}
\]
\[
\Delta E = 1868 \, \text{kJ/mol} - 1362 \, \text{kJ/mol} = 506 \, \text{kJ/mol}
\]

4. **Determine if the reaction is endothermic or exothermic**:
- Since the total energy change is positive (506 kJ/mol), this indicates that energy is absorbed during the reaction, making it an **endothermic** reaction.

Thus, the answer is:

**506 kJ/mol, endothermic**.