Molar Mass of Ethanol (C₂H₆O)
Learn how chemists calculate the molar mass of Ethanol (C₂H₆O), with a clear formula breakdown, worked steps, and study notes.
Quick answer
The molar mass of Ethanol (C₂H₆O) is
46.069g/mol
One mole of Ethanol therefore has a mass of 46.069 grams—the value you use for stoichiometry and laboratory preparation.
Reviewed for educational accuracy · Accuracy policy
- CAS Registry Number
- 64-17-5
- PubChem CID
- 702
- SMILES
- CCO
Step-by-step calculation
Let's find the molar mass of Ethanol (C₂H₆O) together—step by step, as if you are seeing the formula for the first time.
Step 1 — Look at the chemical formula
The formula is C₂H₆O. Each letter stands for an element. The little number after a letter (the subscript) tells you how many atoms of that element are in one molecule or formula unit.
- 2 Carbon atoms (C)
- 6 Hydrogen atoms (H)
- 1 Oxygen atom (O)
Step 2 — Look up each atomic mass
Atomic mass comes from the periodic table. It is the average mass of one mole of atoms of that element, in grams per mole (g/mol). Think of it as the "price tag" for one mole of that element.
- Carbon (C) = 12.011 g/mol
- Hydrogen (H) = 1.008 g/mol
- Oxygen (O) = 15.999 g/mol
Step 3 — Multiply atoms × atomic mass
Why multiply? If one oxygen atom "costs" about 16 g/mol, then two oxygen atoms cost twice as much. Each element's contribution is: number of atoms × atomic mass.
- 2 × 12.011 = 24.022 g/mol (Carbon)
- 6 × 1.008 = 6.048 g/mol (Hydrogen)
- 1 × 15.999 = 15.999 g/mol (Oxygen)
Step 4 — Add the contributions
Why add? The molar mass of the whole compound is simply the total mass of every atom in the formula. Add each element's contribution:
24.022 + 6.048 + 15.999 = 46.069 g/mol
Step 5 — Final answer
Molar mass of Ethanol = 46.069 g/mol
That means one mole of Ethanol (C₂H₆O) has a mass of about 46.07 grams.
Quick summary
Read the formula → count atoms → look up atomic masses → multiply → add → report g/mol. For C₂H₆O, the total is 46.069 g/mol.
Common beginner mistakes
- Confusing ethanol with methanol or isopropanol.
- Using wrong formula C₂H₆O without specifying which isomer (dimethyl ether has same formula).
- Forgetting combustion needs 3 O₂ per ethanol, not 2.
Memory trick
Write C₂H₅OH in exams to clarify alcohol vs. ether isomer.
Mini practice
Without looking above, list the atoms in C₂H₆O and write one multiplication line for the heaviest element. Then check your work against Step 3.
Real-world example
If a recipe asks for 0.100 mol of Ethanol, mass needed = 0.100 × 46.069 = 4.607 g. That is how chemists turn a mole amount into a weighable sample.
Atomic contribution table
Each row shows how much mass one element contributes to the total for C₂H₆O.
| Element | Atoms | Atomic mass | Contribution | Mass % |
|---|---|---|---|---|
| C | 2 | 12.011 | 24.022 g/mol | 52.1% |
| H | 6 | 1.008 | 6.048 g/mol | 13.1% |
| O | 1 | 15.999 | 15.999 g/mol | 34.7% |
| Total molar mass | 46.069 g/mol | 100% | ||
Mass contribution chart
Count every atom in this formula, multiply by atomic mass, then add. That total is the molar mass used in lab weighing.
Download study sheets
Save a printable summary, revision sheet, practice worksheet, or laboratory reference for Ethanol (C₂H₆O).
Practice this calculation
Without looking above, write the atom count for C₂H₆O, then compute the molar mass. Check your answer against 46.069 g/mol.
Next challenge: how many grams are in 0.250 mol of Ethanol? Multiply 0.250 × 46.069 to get 11.517 g.
Physical and chemical properties
Physical properties
| Appearance | Colorless volatile liquid |
| Color | Colorless |
| Odor | Characteristic alcoholic odor |
| State (STP) | Liquid |
| Density | 0.789 g/cm³ at 20 °C |
| Melting point | −114.1 °C |
| Boiling point | 78.37 °C |
| Solubility | Miscible with water and many organic solvents |
| Crystal structure | Not commonly crystallized; forms glasses at low temperature |
Chemical properties
| Classification | Primary alcohol / aliphatic alcohol |
| Family | Alcohols (two-carbon) |
| Polarity | Polar (hydroxyl group, hydrogen bonding) |
| Geometry | Tetrahedral around both carbons and oxygen |
| Oxidation states | C: −3 (methyl) and −1 (carbinol carbon) |
Applications
Industrial uses
- Biofuel blending with gasoline (E10, E85)
- Solvent for perfumes, varnishes, and pharmaceutical formulations
- Hand sanitizer active ingredient (60–80% with water)
- Extraction solvent for botanical compounds
Laboratory uses
- General-purpose polar protic solvent
- Preservative and fixative for biological specimens
- Recrystallization solvent for organic compounds
Metabolite of carbohydrate fermentation; psychoactive substance affecting CNS GABA receptors; antiseptic at 70% concentration (optimal water content aids membrane penetration).
Preparation and production
Fermentation of sugars by Saccharomyces cerevisiae, followed by distillation. Synthetic route: hydration of ethylene: C₂H₄ + H₂O → C₂H₅OH (H₃PO₄ or zeolite catalyst, ~300 °C).
Global ethanol production exceeds 100 billion liters annually, led by USA (corn) and Brazil (sugarcane).
Important reactions of Ethanol
C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O
- Reaction type
- Combustion
- Conditions
- Ignition, excess oxygen
- Explanation
- Complete oxidation of ethanol releases ~1371 kJ/mol; basis of ethanol fuel energy content.
- Products
- Carbon dioxide and water
- Why it matters
- Biofuel energy, calorimetry experiments
Related ideas: Combustion · Thermochemistry · Renewable energy
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂
- Reaction type
- Alcoholic fermentation
- Conditions
- Yeast, anaerobic, ~30 °C
- Explanation
- Glycolysis followed by pyruvate decarboxylation and alcohol dehydrogenase reduction produces ethanol and CO₂.
- Products
- Ethanol and carbon dioxide
- Why it matters
- Beverage production, biofuel
Related ideas: Fermentation · Biochemistry · Enzymes
C₂H₅OH → C₂H₄ + H₂O
- Reaction type
- Dehydration (elimination)
- Conditions
- Concentrated H₂SO₄, 170 °C
- Explanation
- Acid-catalyzed elimination of water forms ethylene; at 140 °C diethyl ether forms instead.
- Products
- Ethene (ethylene) and water
- Why it matters
- Ethylene production, teaching elimination vs. substitution
Related ideas: Elimination reactions · Alkenes · Acid catalysis
C₂H₅OH + CH₃COOH ⇌ CH₃COOC₂H₅ + H₂O
- Reaction type
- Esterification (Fischer)
- Conditions
- Acid catalyst (H₂SO₄), heat
- Explanation
- Ethanol reacts with acetic acid to form ethyl acetate ester and water in reversible equilibrium.
- Products
- Ethyl acetate and water
- Why it matters
- Solvent production, ester chemistry introduction
Related ideas: Esterification · Equilibrium · Functional groups
History and discovery
Fermentation of grain and fruit is among oldest chemical processes (~7000 BCE evidence). Lavoisier analyzed ethanol composition. Pasteur connected yeast to fermentation (1857). Industrial synthetic ethanol from ethylene developed in the 20th century.
Ancient fermentation predates written history; molecular composition clarified by Lavoisier and Gay-Lussac in the 18th–19th centuries.
Interesting facts
- Ethanol molar mass 46.07 g/mol — one mole ≈ 58 mL (density 0.789 g/mL).
- 70% ethanol disinfects better than 95% because water helps denature proteins and penetrate cell membranes.
- Absolute ethanol (100%) is hygroscopic and quickly absorbs water from air.
- Ethanol fuel has lower energy density (~21 MJ/L) than gasoline (~34 MJ/L).
Comparison with similar compounds
Ethanol (46.07 g/mol) and dimethyl ether (46.07 g/mol) are constitutional isomers — same molar mass, different properties (alcohol vs. gas at STP).
Storage, handling, and safety
Store in flame-resistant cabinets, away from ignition sources. Airtight containers prevent evaporation and water absorption. Denatured ethanol contains additives (methanol, bitterants) to prevent consumption.
Highly flammable (flash point 13 °C). No open flames. Ventilate well. Avoid ingestion and prolonged skin contact (defatting).
Flammable liquid; toxic by ingestion; CNS depressant. 70% aqueous ethanol is effective disinfectant but 100% is less effective against microbes.
- Fire hazard — vapors heavier than air travel to ignition sources
- Acute toxicity by ingestion (alcohol poisoning)
- Eye irritation
- Chronic exposure: liver damage (metabolic concern, not lab exposure)
Classification: GHS: Flam. Liq. 2, Eye Irrit. 2
Exam notes and student tips
Exam notes
- Molar mass C₂H₅OH = 2(12.01) + 6(1.008) + 16.00 = 46.07 g/mol.
- Combustion: C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O.
- Functional group: alcohol (–OH); can form hydrogen bonds.
- Distinguish from methanol (CH₃OH, 32.04 g/mol) — methanol is toxic.
Student tips
- Write C₂H₅OH in exams to clarify alcohol vs. ether isomer.
- Link fermentation equation to glucose molar mass (180.16) for yield calculations.
- Remember 46 g/mol for BAC conversion problems.
Common mistakes
- Confusing ethanol with methanol or isopropanol.
- Using wrong formula C₂H₆O without specifying which isomer (dimethyl ether has same formula).
- Forgetting combustion needs 3 O₂ per ethanol, not 2.
Misconceptions
- Ethanol is not a hydrocarbon — it contains oxygen (hydroxyl group).
- Higher proof alcohol does not freeze easily because of depressed freezing point, not absence of water.
- Hand sanitizer needs water content — pure ethanol is less effective as disinfectant.
Practice questions
1. Calculate the molar mass of ethanol (C₂H₅OH).
Show answer
2(12.01) + 6(1.008) + 16.00 = 46.07 g/mol
2. What mass of ethanol from fermentation of 180 g glucose (100% yield)?
Show answer
180 g glucose = 1 mol → 2 mol ethanol = 2 × 46.07 = 92.14 g
3. Why is 70% ethanol used as disinfectant instead of 100%?
Show answer
Water co-solvent denatures proteins and improves penetration through microbial cell walls.
4. How many moles of O₂ for complete combustion of 46 g ethanol?
Show answer
46 g = 1 mol ethanol; needs 3 mol O₂ = 96 g
Frequently asked questions about Ethanol
46.07 g/mol.
Chemistry of Ethanol
The sections above give the number you need for calculations. Here we look more closely at how Ethanol (C₂H₆O) behaves chemically—so the molar mass connects to real reactions, properties, and laboratory practice.
Ethanol (C₂H₅OH) is a two-carbon alcohol with molar mass 46.07 g/mol, featuring a hydroxyl group on a sp³-hybridized carbon. It is fully miscible with water in all proportions due to hydrogen bonding between ethanol's OH and water molecules — a property exploited in alcoholic beverages, disinfectants, and solvent systems.
Ethanol is produced biologically by yeast fermentation: C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂. Industrial bioethanol from corn and sugarcane serves as gasoline additive (E10, E85) and potential renewable fuel. Blood alcohol concentration (BAC) is measured in mg/dL or ‰; ethanol distributes in total body water and is metabolized primarily by alcohol dehydrogenase to acetaldehyde, then aldehyde dehydrogenase to acetate.
C₂H₆O can also be written C₂H₅OH to emphasize the hydroxyl functional group. The formula shows two carbons, six hydrogens, and one oxygen — but only one O–H bond (the hydroxyl proton is acidic, pKa ≈ 16, far weaker than carboxylic acids). The ethyl group (–C₂H₅) attaches to the hydroxyl-bearing carbon.
Ethanol undergoes combustion (C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O), dehydration to ethylene (with concentrated H₂SO₄, 170 °C), oxidation to acetaldehyde then acetic acid, and esterification with carboxylic acids (Fischer esterification). It forms hydrogen bonds, lowering freezing point of mixtures — vodka freezes below −20 °C depending on proof.
Fermentation biochemistry: from sugar to ethanol
Alcoholic fermentation is a multi-step anaerobic biochemical pathway in which yeast first breaks down glucose into pyruvate via glycolysis, then decarboxylates pyruvate to acetaldehyde (releasing CO₂), and finally reduces acetaldehyde to ethanol using the enzyme alcohol dehydrogenase, regenerating the NAD⁺ needed to keep glycolysis running without oxygen. This pathway exists in yeast primarily as a way to sustain energy metabolism under anaerobic conditions, with ethanol and CO₂ as byproducts rather than the biological 'goal' — humans have simply learned to harvest and concentrate this metabolic byproduct for beverages and fuel.
Distillation: separating ethanol from fermented wash
Because ethanol (boiling point 78.4 °C) and water (100 °C) have different volatilities, distillation can concentrate ethanol beyond the roughly 15% maximum achievable by fermentation alone (higher concentrations become toxic to the yeast producing it). However, ethanol and water form an azeotrope at about 95.6% ethanol by mass, at which the vapor and liquid compositions become identical, so ordinary distillation cannot exceed this concentration; producing anhydrous (100%) ethanol requires additional techniques such as azeotropic distillation with a third component, molecular sieve dehydration, or membrane pervaporation.
Ethanol as fuel: energy content and blending
As a biofuel, ethanol is blended into gasoline at various concentrations (E10 at 10%, E85 at up to 85%) to reduce petroleum consumption and, depending on feedstock and production method, potentially lower net lifecycle carbon emissions. Its lower energy density compared to gasoline (about 21 MJ/L versus 34 MJ/L) means ethanol-blended fuels deliver somewhat lower fuel economy per liter, but ethanol's higher octane rating allows higher-compression, more efficient engine designs, partially offsetting the energy density disadvantage in specially tuned flex-fuel vehicles.
Ethanol in beverages: proof, fermentation limits, and congeners
Alcoholic beverage strength is measured as percent alcohol by volume (ABV) or, in some countries, 'proof' (historically twice the ABV in the US system). Beverages relying solely on fermentation — beer, wine — top out around 15–20% ABV because rising ethanol concentration progressively poisons the yeast producing it; higher-proof spirits require distillation to concentrate the ethanol beyond this natural fermentation ceiling. Distillation also concentrates 'congeners' — trace flavor and aroma compounds like esters, higher alcohols, and aldehydes carried over from fermentation — which is why different spirits distilled from different fermented washes have such distinct characteristic flavors despite sharing the same core ethanol molecule.
Ethanol as a laboratory solvent: polarity and versatility
Ethanol's structure — a small nonpolar ethyl group attached to a polar hydroxyl group — gives it intermediate polarity that makes it miscible with both water and many nonpolar organic solvents, a versatility exploited throughout the laboratory as a recrystallization solvent, extraction medium, and cleaning agent for glassware and biological specimens. This same intermediate polarity underlies its use as a protic solvent in reactions requiring hydrogen-bond donation, distinguishing its solvent behavior from purely nonpolar solvents like hexane or purely polar aprotic solvents like DMSO.
Recalculate any formula with the molar mass calculator, compare atoms on the periodic table, or browse more compounds in the organic library.
References and further reading
- PubChem CID 702: Ethanol structure and properties
- NIST Chemistry WebBook: Thermochemical data
- IUPAC: Alcohol nomenclature