---
title: "The Sabatier process is utilized in spacecraft life-support systems to convert carbon dioxide exhaled by the crew into methane and water vapor according to the following balanced equation:  \\[\\text{CO}_2(g) + 4\\,\\text{H}_2(g) \\rightarrow \\text{CH}_4(g) + 2\\,\\text{H}_2\\text{O}(g)\\]  Average bond enthalpies for the chemical bonds involved in this reaction are provided in the table below.  | Bond | Average bond enthalpy (\\(\\text{kJ/mol}\\)) | | :— | :— | | \\(\\text{C}=\\text{O}\\text{ (in }\\text{CO}_2\\text{)}\\) | \\(800\\) | | \\(\\text{H}-\\text{H}\\) | \\(435\\) | | \\(\\text{C}-\\text{H}\\) | \\(415\\) | | \\(\\text{O}-\\text{H}\\) | \\(465\\) |  Based on the data in the table, what is the estimated enthalpy of reaction, \\(\\Delta H^\\circ_{\\text{rxn}}\\), for this process?"
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url: "https://nerd-notes.com/ubq/121497/"
date_modified: "2026-08-23T05:04:50+00:00"
---

# The Sabatier process is utilized in spacecraft life-support systems to convert carbon dioxide exhaled by the crew into methane and water vapor according to the following balanced equation:

\[\text{CO}_2(g) + 4\,\text{H}_2(g) \rightarrow \text{CH}_4(g) + 2\,\text{H}_2\text{O}(g)\]

Average bond enthalpies for the chemical bonds involved in this reaction are provided in the table below.

| Bond | Average bond enthalpy (\(\text{kJ/mol}\)) |
| :— | :— |
| \(\text{C}=\text{O}\text{ (in }\text{CO}_2\text{)}\) | \(800\) |
| \(\text{H}-\text{H}\) | \(435\) |
| \(\text{C}-\text{H}\) | \(415\) |
| \(\text{O}-\text{H}\) | \(465\) |

Based on the data in the table, what is the estimated enthalpy of reaction, \(\Delta H^\circ_{\text{rxn}}\), for this process?

The Sabatier process is utilized in spacecraft life-support systems to convert carbon dioxide exhaled by the crew into methane and water vapor according to the following balanced equation:

\[\text{CO}_2(g) + 4\,\text{H}_2(g) \rightarrow \text{CH}_4(g) + 2\,\text{H}_2\text{O}(g)\]

Average bond enthalpies for the chemical bonds involved in this reaction are provided in the table below.

| Bond | Average bond enthalpy (\(\text{kJ/mol}\)) |
| :--- | :--- |
| \(\text{C}=\text{O}\text{ (in }\text{CO}_2\text{)}\) | \(800\) |
| \(\text{H}-\text{H}\) | \(435\) |
| \(\text{C}-\text{H}\) | \(415\) |
| \(\text{O}-\text{H}\) | \(465\) |

Based on the data in the table, what is the estimated enthalpy of reaction, \(\Delta H^\circ_{\text{rxn}}\), for this process?

- **A.** \(-180 \text{ kJ/mol}_{\text{rxn}}\)
- **B.** \(+180 \text{ kJ/mol}_{\text{rxn}}\)
- **C.** \(+750 \text{ kJ/mol}_{\text{rxn}}\)
- **D.** \(+980 \text{ kJ/mol}_{\text{rxn}}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121497/*