---
title: "A student determines the standard molar enthalpy of combustion, \\(\\Delta H_{\\text{comb}}^\\circ\\), of an unknown liquid fuel using a bomb calorimeter. In the calibration trial, the student combusts a sample of benzoic acid (\\(\\text{C}_7\\text{H}_6\\text{O}_2\\), molar mass \\(122\\text{ g/mol}\\)), which has a known \\(\\Delta H_{\\text{comb}}^\\circ = -3.20 \\times 10^3\\text{ kJ/mol}\\). In a second trial, the student combusts a sample of the unknown liquid fuel in the same calorimeter. The experimental data collected are shown in the table below.  | Measurement | Calibration trial (benzoic acid) | Fuel trial (unknown fuel) | | :— | :— | :— | | Molar mass of substance (\\(\\text{g/mol}\\)) | \\(122\\) | \\(46.0\\) | | Mass of sample combusted (\\(\\text{g}\\)) | \\(1.22\\) | \\(0.920\\) | | Initial calorimeter temperature (\\(^\\circ\\text{C}\\)) | \\(21.50\\) | \\(22.00\\) | | Final calorimeter temperature (\\(^\\circ\\text{C}\\)) | \\(25.50\\) | \\(25.50\\) |  Based on the data in the table, what is the value of \\(\\Delta H_{\\text{comb}}^\\circ\\) for the unknown liquid fuel?"
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url: "https://nerd-notes.com/ubq/123825/"
date_modified: "2026-09-28T12:30:27+00:00"
---

# A student determines the standard molar enthalpy of combustion, \(\Delta H_{\text{comb}}^\circ\), of an unknown liquid fuel using a bomb calorimeter. In the calibration trial, the student combusts a sample of benzoic acid (\(\text{C}_7\text{H}_6\text{O}_2\), molar mass \(122\text{ g/mol}\)), which has a known \(\Delta H_{\text{comb}}^\circ = -3.20 \times 10^3\text{ kJ/mol}\). In a second trial, the student combusts a sample of the unknown liquid fuel in the same calorimeter. The experimental data collected are shown in the table below.

| Measurement | Calibration trial (benzoic acid) | Fuel trial (unknown fuel) |
| :— | :— | :— |
| Molar mass of substance (\(\text{g/mol}\)) | \(122\) | \(46.0\) |
| Mass of sample combusted (\(\text{g}\)) | \(1.22\) | \(0.920\) |
| Initial calorimeter temperature (\(^\circ\text{C}\)) | \(21.50\) | \(22.00\) |
| Final calorimeter temperature (\(^\circ\text{C}\)) | \(25.50\) | \(25.50\) |

Based on the data in the table, what is the value of \(\Delta H_{\text{comb}}^\circ\) for the unknown liquid fuel?

A student determines the standard molar enthalpy of combustion, \(\Delta H_{\text{comb}}^\circ\), of an unknown liquid fuel using a bomb calorimeter. In the calibration trial, the student combusts a sample of benzoic acid (\(\text{C}_7\text{H}_6\text{O}_2\), molar mass \(122\text{ g/mol}\)), which has a known \(\Delta H_{\text{comb}}^\circ = -3.20 \times 10^3\text{ kJ/mol}\). In a second trial, the student combusts a sample of the unknown liquid fuel in the same calorimeter. The experimental data collected are shown in the table below.

| Measurement | Calibration trial (benzoic acid) | Fuel trial (unknown fuel) |
| :--- | :--- | :--- |
| Molar mass of substance (\(\text{g/mol}\)) | \(122\) | \(46.0\) |
| Mass of sample combusted (\(\text{g}\)) | \(1.22\) | \(0.920\) |
| Initial calorimeter temperature (\(^\circ\text{C}\)) | \(21.50\) | \(22.00\) |
| Final calorimeter temperature (\(^\circ\text{C}\)) | \(25.50\) | \(25.50\) |

Based on the data in the table, what is the value of \(\Delta H_{\text{comb}}^\circ\) for the unknown liquid fuel?

- **A.** \(-1.40 \times 10^3\text{ kJ/mol}\)
- **B.** \(-7.00 \times 10^2\text{ kJ/mol}\)
- **C.** \(-2.80 \times 10^1\text{ kJ/mol}\)
- **D.** \(+1.40 \times 10^3\text{ kJ/mol}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123825/*