---
title: "A student investigates the thermodynamics of the industrial synthesis of ammonia from its elements in the gas phase, represented by the balanced chemical equation below.  \\[ \\text{N}_2(g) + 3\\,\\text{H}_2(g) \\rightarrow 2\\,\\text{NH}_3(g) \\]  The table below provides the average bond enthalpies for the chemical bonds involved in the reaction.  | Bond | Average bond enthalpy (\\(\\text{kJ/mol}\\)) | | :— | :— | | \\(\\text{N}\\equiv\\text{N}\\) | \\(946\\) | | \\(\\text{H}-\\text{H}\\) | \\(436\\) | | \\(\\text{N}-\\text{H}\\) | \\(391\\) |  Based on the information in the table, what is the estimated standard enthalpy change of the reaction, \\(\\Delta H^\\circ_{\\text{rxn}}\\)?"
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url: "https://nerd-notes.com/ubq/121443/"
date_modified: "2026-08-23T05:02:31+00:00"
---

# A student investigates the thermodynamics of the industrial synthesis of ammonia from its elements in the gas phase, represented by the balanced chemical equation below.

\[ \text{N}_2(g) + 3\,\text{H}_2(g) \rightarrow 2\,\text{NH}_3(g) \]

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

| Bond | Average bond enthalpy (\(\text{kJ/mol}\)) |
| :— | :— |
| \(\text{N}\equiv\text{N}\) | \(946\) |
| \(\text{H}-\text{H}\) | \(436\) |
| \(\text{N}-\text{H}\) | \(391\) |

Based on the information in the table, what is the estimated standard enthalpy change of the reaction, \(\Delta H^\circ_{\text{rxn}}\)?

A student investigates the thermodynamics of the industrial synthesis of ammonia from its elements in the gas phase, represented by the balanced chemical equation below.

\[ \text{N}_2(g) + 3\,\text{H}_2(g) \rightarrow 2\,\text{NH}_3(g) \]

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

| Bond | Average bond enthalpy (\(\text{kJ/mol}\)) |
| :--- | :--- |
| \(\text{N}\equiv\text{N}\) | \(946\) |
| \(\text{H}-\text{H}\) | \(436\) |
| \(\text{N}-\text{H}\) | \(391\) |

Based on the information in the table, what is the estimated standard enthalpy change of the reaction, \(\Delta H^\circ_{\text{rxn}}\)?

- **A.** \(-92 \text{ kJ/mol}_{\text{rxn}}\)
- **B.** \(-46 \text{ kJ/mol}_{\text{rxn}}\)
- **C.** \(+46 \text{ kJ/mol}_{\text{rxn}}\)
- **D.** \(+92 \text{ kJ/mol}_{\text{rxn}}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121443/*