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title: "Hydrazine, \\(\\text{N}_2\\text{H}_4\\), decomposes into nitrogen gas and hydrogen gas according to the following equation.  \\[\\text{N}_2\\text{H}_4\\text{(g)} \\rightarrow \\text{N}_2\\text{(g)} + 2\\,\\text{H}_2\\text{(g)}\\]  The table below provides average bond energies for the bonds involved in the reaction.  | Bond | Average bond energy (\\(\\text{kJ/mol}\\)) | | :— | :— | | \\(\\text{N}-\\text{N}\\) | \\(160\\) | | \\(\\text{N}-\\text{H}\\) | \\(390\\) | | \\(\\text{N}\\equiv\\text{N}\\) | \\(950\\) | | \\(\\text{H}-\\text{H}\\) | \\(435\\) |  Based on the data in the table, which of the following correctly predicts and explains whether the decomposition reaction is endothermic or exothermic?"
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url: "https://nerd-notes.com/ubq/123770/"
date_modified: "2026-09-28T12:30:15+00:00"
---

# Hydrazine, \(\text{N}_2\text{H}_4\), decomposes into nitrogen gas and hydrogen gas according to the following equation.

\[\text{N}_2\text{H}_4\text{(g)} \rightarrow \text{N}_2\text{(g)} + 2\,\text{H}_2\text{(g)}\]

The table below provides average bond energies for the bonds involved in the reaction.

| Bond | Average bond energy (\(\text{kJ/mol}\)) |
| :— | :— |
| \(\text{N}-\text{N}\) | \(160\) |
| \(\text{N}-\text{H}\) | \(390\) |
| \(\text{N}\equiv\text{N}\) | \(950\) |
| \(\text{H}-\text{H}\) | \(435\) |

Based on the data in the table, which of the following correctly predicts and explains whether the decomposition reaction is endothermic or exothermic?

Hydrazine, \(\text{N}_2\text{H}_4\), decomposes into nitrogen gas and hydrogen gas according to the following equation.

\[\text{N}_2\text{H}_4\text{(g)} \rightarrow \text{N}_2\text{(g)} + 2\,\text{H}_2\text{(g)}\]

The table below provides average bond energies for the bonds involved in the reaction.

| Bond | Average bond energy (\(\text{kJ/mol}\)) |
| :--- | :--- |
| \(\text{N}-\text{N}\) | \(160\) |
| \(\text{N}-\text{H}\) | \(390\) |
| \(\text{N}\equiv\text{N}\) | \(950\) |
| \(\text{H}-\text{H}\) | \(435\) |

Based on the data in the table, which of the following correctly predicts and explains whether the decomposition reaction is endothermic or exothermic?

- **A.** The reaction is endothermic because more energy is required to break the one \(\text{N}-\text{N}\) single bond and four \(\text{N}-\text{H}\) single bonds in \(\text{N}_2\text{H}_4\) than is released when forming the one \(\text{N}\equiv\text{N}\) triple bond and two \(\text{H}-\text{H}\) single bonds.
- **B.** The reaction is exothermic because more energy is released when forming the one \(\text{N}\equiv\text{N}\) triple bond and two \(\text{H}-\text{H}\) single bonds than is required to break the one \(\text{N}-\text{N}\) single bond and four \(\text{N}-\text{H}\) single bonds in \(\text{N}_2\text{H}_4\).
- **C.** The reaction is endothermic because forming the strong \(\text{N}\equiv\text{N}\) triple bond in \(\text{N}_2\) requires a large input of energy (\(950\text{ kJ/mol}\)).
- **D.** The reaction is exothermic because breaking the relatively weak \(\text{N}-\text{N}\) single bond in \(\text{N}_2\text{H}_4\) directly releases energy (\(160\text{ kJ/mol}\)) to the surroundings.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123770/*