Ethanol combustion and its solvent and fuel uses
Connect ethanol's two required uses with energy release and dissolving behaviour without assuming burning and dissolving are the same process.
Core and Extended · Chemistry 0620, 2026–2028. Manufacture comparisons, ethanol oxidation and esterification are developed in Extended lessons.
Before you begin
- Count all atoms in C₂H₅OH and distinguish physical from chemical changes.
- Recognise carbon dioxide and water as complete-combustion products.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does a solvent do in the stated solution model?
What you will learn
- Describe ethanol combustion and balance its complete-combustion equation.
- State ethanol's uses as a solvent and as a fuel.
The fuel use depends on chemical energy release
Ethanol is used as a fuel because its combustion releases energy. Complete combustion with sufficient oxygen forms carbon dioxide and water: C₂H₅OH+3O₂→2CO₂+3H₂O. Count the oxygen already inside ethanol: one in ethanol plus six from O₂ makes seven, matching four in CO₂ and three in water.
Limited oxygen can lead to incomplete combustion, so the complete equation must be matched with the stated oxygen condition. Being oxygen-containing does not mean ethanol cannot burn, and calling it a fuel does not by itself prove zero greenhouse-gas emissions. Actual climate comparisons depend on production and use as well as combustion.
The solvent use depends on dissolving
A solvent dissolves another substance to make a solution. Ethanol is used as a solvent, for example in some perfumes and inks. In a supplied application, judge whether the substance dissolves and whether the solvent suits the process; dissolving is not the same as combusting that substance.
Solvent and fuel describe uses, not new homologous-series names. Ethanol retains its alcohol structure when simply used as the solvent in the stated physical model, whereas complete combustion changes its atoms into carbon dioxide and water. Its flammability also matters when a process uses it as a solvent; solvent does not imply non-flammable.
Pause and explain
How much O₂ appears per ethanol in its complete-combustion equation?
Worked example
State ethanol's two required uses and balance complete combustion by counting oxygen already in the molecule.
Show the worked solution
- Its required uses are solvent and fuel.
- Two C give 2CO₂ and six H give 3H₂O, requiring seven product O atoms.
- One O comes from ethanol, leaving six supplied by 3O₂: C₂H₅OH+3O₂→2CO₂+3H₂O.
Answer Solvent and fuel; C₂H₅OH+3O₂→2CO₂+3H₂O for complete combustion.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain one solvent use and one fuel use of ethanol.
Give me a hint
Connect each use with the relevant behaviour, rather than just naming a product.
Compare my reasoning
- As a solvent in a suitable ink or perfume, ethanol dissolves substances to make a solution.
- As a fuel, it releases energy when it combusts.
- Dissolving and complete combustion are different processes; only the latter forms the stated CO₂ and H₂O products.
Solvent: dissolving suitable ink/perfume substances. Fuel: combustion releases energy.
Look for these in your work
- Both required uses appear.
- Each is linked to the correct behaviour.
Balance complete ethanol combustion and check all three element totals.
Give me a hint
The OH adds one H and one O before external oxygen is counted.
Compare my reasoning
- C₂H₅OH totals C₂H₆O; use 2CO₂ and 3H₂O.
- Products total C₂H₆O₇, so add six O atoms as 3O₂.
- C₂H₅OH+3O₂→2CO₂+3H₂O balances C₂, H₆ and O₇.
C₂H₅OH+3O₂→2CO₂+3H₂O; both sides C₂H₆O₇.
Look for these in your work
- Ethanol's own oxygen is included.
- All element totals match without changing subscripts.
A student says dissolving a perfume ingredient in ethanol destroys its carbon, and burning ethanol creates no carbon dioxide because it already contains oxygen. Assess both claims.
Give me a hint
Check physical dissolution separately from combustion's atom products.
Compare my reasoning
- Dissolving in the stated solvent model forms a solution without deleting the ingredient's carbon atoms.
- Complete ethanol combustion converts its two carbons into 2CO₂.
- The ethanol oxygen is included in balancing; it does not remove the carbon dioxide product.
Dissolving does not delete carbon; complete ethanol combustion still produces carbon dioxide and water.
Look for these in your work
- The physical and chemical processes are separated.
- The carbon and oxygen claims are corrected by atom accounting.
Common mistakes
- Forgetting ethanol's own oxygen when balancing combustion.
- Calling dissolving a pigment the same chemical reaction as burning.
- Assuming an alcohol's oxygen makes it unable to burn.
- Equating fuel use with a guaranteed zero-emission process.
What can you explain now?
Which two ethanol uses are required?
Compare with the explanation
A solvent and a fuel.
Dissolving and releasing energy through combustion explain different applications.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
State ethanol's two uses and balance combustion from a blank page, including the oxygen within the alcohol.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.