---
title: "A student compares three fuels to determine which releases the greatest amount of heat per gram combusted under standard conditions. The complete combustion of each fuel is represented by the general process:  \\[ \\text{Fuel} + \\text{O}_2\\text{(g)} \\rightarrow \\text{CO}_2\\text{(g)} + \\text{H}_2\\text{O(l)} \\]  The table below provides the molar mass and standard molar enthalpy of combustion, \\(\\Delta H^\\circ_{\\text{comb}}\\), for each fuel.  | Fuel | Chemical formula | Molar mass (\\(\\text{g/mol}\\)) | \\(\\Delta H^\\circ_{\\text{comb}}\\) (\\(\\text{kJ/mol}\\)) | | :— | :— | :— | :— | | Methane | \\(\\text{CH}_4\\) | \\(16\\) | \\(-880\\) | | Ethanol | \\(\\text{C}_2\\text{H}_5\\text{OH}\\) | \\(46\\) | \\(-1380\\) | | Octane | \\(\\text{C}_8\\text{H}_{18}\\) | \\(114\\) | \\(-5472\\) |  Which of the following correctly ranks the fuels in order of the quantity of heat released per gram of fuel combusted, from greatest to least?"
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url: "https://nerd-notes.com/ubq/119752/"
date_modified: "2026-08-21T08:12:13+00:00"
---

# A student compares three fuels to determine which releases the greatest amount of heat per gram combusted under standard conditions. The complete combustion of each fuel is represented by the general process:

\[ \text{Fuel} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O(l)} \]

The table below provides the molar mass and standard molar enthalpy of combustion, \(\Delta H^\circ_{\text{comb}}\), for each fuel.

| Fuel | Chemical formula | Molar mass (\(\text{g/mol}\)) | \(\Delta H^\circ_{\text{comb}}\) (\(\text{kJ/mol}\)) |
| :— | :— | :— | :— |
| Methane | \(\text{CH}_4\) | \(16\) | \(-880\) |
| Ethanol | \(\text{C}_2\text{H}_5\text{OH}\) | \(46\) | \(-1380\) |
| Octane | \(\text{C}_8\text{H}_{18}\) | \(114\) | \(-5472\) |

Which of the following correctly ranks the fuels in order of the quantity of heat released per gram of fuel combusted, from greatest to least?

A student compares three fuels to determine which releases the greatest amount of heat per gram combusted under standard conditions. The complete combustion of each fuel is represented by the general process:

\[ \text{Fuel} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O(l)} \]

The table below provides the molar mass and standard molar enthalpy of combustion, \(\Delta H^\circ_{\text{comb}}\), for each fuel.

| Fuel | Chemical formula | Molar mass (\(\text{g/mol}\)) | \(\Delta H^\circ_{\text{comb}}\) (\(\text{kJ/mol}\)) |
| :--- | :--- | :--- | :--- |
| Methane | \(\text{CH}_4\) | \(16\) | \(-880\) |
| Ethanol | \(\text{C}_2\text{H}_5\text{OH}\) | \(46\) | \(-1380\) |
| Octane | \(\text{C}_8\text{H}_{18}\) | \(114\) | \(-5472\) |

Which of the following correctly ranks the fuels in order of the quantity of heat released per gram of fuel combusted, from greatest to least?

- **A.** \(\text{Methane} > \text{ethanol} > \text{octane}\)
- **B.** \(\text{Methane} > \text{octane} > \text{ethanol}\)
- **C.** \(\text{Octane} > \text{ethanol} > \text{methane}\)
- **D.** \(\text{Octane} > \text{methane} > \text{ethanol}\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119752/*