NCERT Class 10 Science | Chapter: Carbon and Its Compounds | Texcellency Book Series

✅ Answer in Brief (For Quick Revision)

Ethanol (C₂H₅OH) and ethanoic acid (CH₃COOH) can be differentiated by both physical and chemical properties. Physically — they differ in smell (alcoholic vs sour vinegar), boiling point (78°C vs 118°C), freezing point (–114°C vs 16.6°C), and nature (neutral vs acidic). Chemically — ethanoic acid turns blue litmus red and fizzes with Na₂CO₃ (releasing CO₂), while ethanol does neither. These differences reflect the fundamental chemical difference between them — ethanol has a neutral –OH group while ethanoic acid has an acidic –COOH group.

🏭 The Wine and Vinegar Analogy

Ethanol and ethanoic acid are not strangers — they are chemically related. Ethanoic acid is literally made FROM ethanol by oxidation. When wine (which contains ethanol) is left open, bacteria in air oxidise the ethanol → ethanoic acid. The wine goes sour and becomes vinegar. So the difference between ethanol and ethanoic acid is the difference between fresh wine and old sour vinegar — and you can tell them apart by smell alone even before doing any chemistry.

🔵 Ethanol → smells like wine, whisky, spirit — the familiar alcoholic smell 🔵 Ethanoic acid → smells like vinegar — sharp, sour, pungent — the smell that makes your eyes water

But in chemistry, we need more than smell. We need precise physical measurements and confirmed chemical reactions. Here is the complete differentiation.

🔴 Physical Properties — Differentiation

Property 1 — Smell (Most Obvious Physical Difference): 🔵 Ethanol: Pleasant, characteristic alcoholic smell — the smell of wine, beer, spirit 🔵 Ethanoic acid: Sharp, pungent, sour smell — the smell of vinegar (which is 5–8% ethanoic acid in water) 🔵 Verdict: Easily distinguishable by smell alone ✅

Property 2 — Taste: 🔵 Ethanol: Burning, warming sensation — the taste characteristic of alcoholic beverages 🔵 Ethanoic acid: Intensely sour taste — the sour taste of vinegar 🔵 Note: In laboratory settings, tasting chemicals is NOT recommended. This is only for understanding — vinegar is the safe real-life example of ethanoic acid.

Property 3 — Boiling Point: 🔵 Ethanol: boiling point = 78.4°C 🔵 Ethanoic acid: boiling point = 117.9°C 🔵 Ethanoic acid boils at a significantly higher temperature — nearly 40°C higher — because its molecules form stronger intermolecular hydrogen bonds (two –COOH groups can hydrogen bond with each other, forming dimers) 🔵 Verdict: A clear measurable physical difference ✅

Property 4 — Freezing/Melting Point (The Glacial Acetic Acid Fact — Exam Gold): 🔵 Ethanol: freezing point = –114.1°C — remains liquid at all normal temperatures, even cold weather 🔵 Ethanoic acid: freezing point = 16.6°C — this is just BELOW room temperature 🔵 This means: on a cold winter day (when temperature drops below 16.6°C), pure ethanoic acid can solidify into a colourless ice-like solid in the laboratory 🔵 This solidified form of pure ethanoic acid is called “Glacial Acetic Acid” — because it resembles glacial ice 🔵 This is a remarkable and exam-favourite property — ethanol would NEVER solidify under normal conditions, but ethanoic acid can solidify on a cold day 🔵 Verdict: Dramatic, measurable, and memorable physical difference ✅

Property 5 — Nature (Acidic vs Neutral): 🔵 Ethanol: neutral — pH ≈ 7 — does not change litmus 🔵 Ethanoic acid: acidic — pH ≈ 2.9 to 3.5 (depending on concentration) — turns blue litmus red 🔵 Though this is detected by a chemical indicator (litmus), the underlying difference (acidic vs neutral nature) is a fundamental property of the substances themselves 🔵 Verdict: Most important and most exam-relevant physical/chemical property difference ✅

Property 6 — Density: 🔵 Ethanol: 0.789 g/mL at 20°C 🔵 Ethanoic acid: 1.049 g/mL at 20°C 🔵 Ethanoic acid is denser than ethanol — and denser than water (1.0 g/mL) 🔵 Verdict: Measurable laboratory difference ✅

🔶 Chemical Properties — Differentiation

Chemical Test 1 — Litmus Paper Test (Quickest Chemical Test):

Procedure: Dip a strip of blue litmus paper into each substance.

🔵 Ethanol + blue litmus → no colour change — ethanol is neutral (–OH group does not release H⁺ ions) 🔵 Ethanoic acid + blue litmus → turns RED — ethanoic acid is acidic (–COOH group releases H⁺ ions: CH₃COOH ⇌ CH₃COO⁻ + H⁺)

Verdict: Blue litmus test is a simple, instant differentiating test ✅

Chemical Test 2 — Sodium Carbonate / Sodium Bicarbonate Test (Most Important — NCERT Expected):

Procedure: Add a few drops of each substance to sodium carbonate (Na₂CO₃) or sodium bicarbonate (NaHCO₃) solution in separate test tubes. Observe.

🔵 Ethanol + Na₂CO₃ → No reaction. No fizzing. No gas evolved. 🔵 Ethanoic acid + Na₂CO₃ → Brisk effervescence. CO₂ gas evolved. Fizzing observed.

Chemical equation: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑ (Ethanoic acid + Sodium carbonate → Sodium ethanoate + Water + Carbon dioxide)

To confirm CO₂: pass the gas through lime water → lime water turns milky: CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O

Why ethanol does not react: ethanol is neutral — it has no acidic H⁺ to donate to the carbonate ion. Na₂CO₃ is a base — it only reacts with acids, not with neutral substances.

Verdict: The most reliable and NCERT-recommended chemical differentiating test ✅

Chemical Test 3 — Reaction with NaOH (Sodium Hydroxide):

Procedure: Add NaOH solution to each substance.

🔵 Ethanol + NaOH → No reaction — ethanol is not acidic enough to react with NaOH under normal conditions 🔵 Ethanoic acid + NaOH → Neutralisation reaction — ethanoic acid reacts with NaOH (a base) to form sodium ethanoate (a salt) and water:

CH₃COOH + NaOH → CH₃COONa + H₂O (Ethanoic acid + Sodium hydroxide → Sodium ethanoate + Water)

This is a standard acid-base neutralisation. Ethanol being neutral does not undergo this reaction.

Verdict: Another clear chemical differentiating test ✅

Chemical Test 4 — Esterification Test (The Sweet Smell Test):

Procedure: To a sample of the unknown substance, add ethanol (if testing for acid) or ethanoic acid (if testing for alcohol) along with a few drops of concentrated H₂SO₄ (catalyst). Warm gently and pour into water. Smell carefully.

🔵 Ethanoic acid + ethanol + conc. H₂SO₄ + heat → sweet, fruity smell (ethyl ethanoate ester formed): CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O (Ethanoic acid + Ethanol → Ethyl ethanoate + Water)

🔵 Ethanol alone + conc. H₂SO₄ + heat → no sweet ester smell (without a carboxylic acid partner, no ester forms under these conditions)

Verdict: The esterification test confirms the presence of the carboxylic acid group in ethanoic acid ✅

Important note on sodium metal test: BOTH ethanol and ethanoic acid react with sodium metal to produce hydrogen gas. Therefore the sodium metal test CANNOT be used to differentiate them — it is not a valid distinguishing test for this pair. Do not use it in your answer.

🔷 The Root Cause — Why They Behave So Differently

All the physical and chemical differences between ethanol and ethanoic acid trace back to ONE fundamental structural difference:

🔵 Ethanol has –OH (hydroxyl group): This –OH does NOT release H⁺ in water. Ethanol is neutral. The –OH can form hydrogen bonds with water (explaining its high miscibility with water) but it does not donate protons to bases or indicators.

🔵 Ethanoic acid has –COOH (carboxyl group): The –COOH IS acidic — it releases H⁺ in water: CH₃COOH ⇌ CH₃COO⁻ + H⁺ This H⁺ is what turns litmus red, reacts with Na₂CO₃ to give CO₂, neutralises NaOH, and makes ethanoic acid sour to taste.

The –COOH group is acidic because the C=O part of it pulls electron density away from the –OH part, making it easier for the –OH to release its H⁺ as a proton. In plain ethanol (–OH only), there is no C=O pulling electrons away — so the H is not released as H⁺. This is why alcohols are neutral and carboxylic acids are acidic.

🔴 Real-Life Connections

🔵 Ethanol in daily life: wine, beer, whisky, brandy (alcoholic beverages) — all contain ethanol as the active ingredient. Also used as a solvent, antiseptic (sanitisers), and fuel (biofuel). 🔵 Ethanoic acid in daily life: vinegar (5–8% ethanoic acid in water) — used in cooking, pickling, preserving food. Also used industrially to make plastics (PET — polyethylene terephthalate), synthetic fibres, and pharmaceuticals (aspirin is acetylsalicylic acid — made using ethanoic acid/acetic anhydride). 🔵 Glacial acetic acid in labs: pure ethanoic acid used as a solvent and reagent in chemical synthesis. Its freezing at 16.6°C is a well-known laboratory phenomenon. 🔵 The oxidation connection: ethanol → ethanoic acid is the same reaction that sours wine into vinegar. KMnO₄ or K₂Cr₂O₇ in the lab does in minutes what bacteria do in days.

📊 Master Comparison Table — Ethanol vs Ethanoic Acid

Name: Ethanol vs Ethanoic Acid Formula: C₂H₅OH vs CH₃COOH Functional group: –OH (hydroxyl) vs –COOH (carboxyl) Nature: Neutral (pH ≈ 7) vs Acidic (pH ≈ 2.9–3.5) Smell: Alcoholic (wine/spirit) vs Sharp, sour (vinegar) Boiling point: 78.4°C vs 117.9°C Freezing point: –114.1°C vs 16.6°C (glacial acetic acid) Density: 0.789 g/mL vs 1.049 g/mL Blue litmus test: No change vs Turns RED Na₂CO₃ test: No reaction vs Brisk fizzing (CO₂ released) NaOH reaction: No reaction vs Neutralisation (forms CH₃COONa + H₂O) Esterification: Forms ester WITH acid vs Forms ester WITH alcohol Na metal test: Reacts (H₂ gas) vs Also reacts (H₂ gas) — NOT a distinguishing test Real-life example: Wine, sanitiser, biofuel vs Vinegar, food preservative Made from: Fermentation of sugars vs Oxidation of ethanol

🎵 Rhyme to Remember

“Ethanol smells like wine so fine, Neutral nature — it’s doing fine,* Blue litmus? No change — it just walks past,* Na₂CO₃? No fizz — no reaction, no blast!* But ethanoic acid — sharp like a knife,* The sour smell of vinegar — the taste of strife!* Blue litmus turns RED — it’s acidic, you see,* Na₂CO₃ fizzes — CO₂ breaks free!* Boils at 118, freezes at 16.6 degrees,* Glacial acetic acid — solid on cold days with ease!”*

🧩 Mnemonics

🔵 “ETHANOL = Easy going, Neutral, No fizz with Na₂CO₃” — the three key facts about ethanol in one phrase. 🔵 “ETHANOIC = Energetically Acidic, CO₂ with Na₂CO₃, Turns litmus Red, Neutralises NaOH, Esterifies, Glacial at 16.6°C” — every key property in the name. 🔵 “–OH = Only Hangs on, never lets go of H⁺ (neutral). –COOH = Constantly Outputs OH-stripped H⁺ (acidic).” 🔵 “Glacial acetic acid = ethanoic acid freezes at 16.6°C = looks like ICE in cold lab.” 🔵 “Na₂CO₃ test: ACID fizzes, ALCOHOL misses” — from our earlier post — applies perfectly here too.

✅ Exam-Ready Answer (Write This in Board Exam)

How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

A. Physical Properties:

1. Smell: Ethanol has a characteristic alcoholic smell (like wine or spirit). Ethanoic acid has a sharp, sour, pungent smell (like vinegar).

2. Boiling Point: Ethanol boils at 78.4°C. Ethanoic acid boils at a higher temperature — 117.9°C — due to stronger intermolecular hydrogen bonding.

3. Freezing Point: Ethanol freezes at –114.1°C (never solidifies under normal conditions). Ethanoic acid freezes at 16.6°C — pure ethanoic acid can solidify into an ice-like solid on cold days. This solid form is called Glacial Acetic Acid.

4. Nature: Ethanol is neutral (pH ≈ 7). Ethanoic acid is acidic (pH ≈ 2.9–3.5).

B. Chemical Properties:

1. Litmus Test: Ethanol does not change the colour of blue litmus paper (neutral). Ethanoic acid turns blue litmus red (acidic).

2. Sodium Carbonate Test (Na₂CO₃ Test): 🔵 Ethanol + Na₂CO₃ → No reaction. No fizzing. 🔵 Ethanoic acid + Na₂CO₃ → Brisk effervescence. CO₂ gas evolved, which turns lime water milky. 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑

3. Reaction with NaOH: 🔵 Ethanol + NaOH → No reaction. 🔵 Ethanoic acid + NaOH → Neutralisation: CH₃COOH + NaOH → CH₃COONa + H₂O

4. Esterification Test: 🔵 When ethanoic acid is mixed with ethanol in the presence of conc. H₂SO₄ and heated, a sweet-smelling ester (ethyl ethanoate) is formed: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O 🔵 Ethanol alone does not produce this sweet smell.

📌 Key Points Checklist

✅ Ethanol = C₂H₅OH, –OH group, neutral, pH ≈ 7, alcoholic smell, boils at 78.4°C, freezes at –114.1°C ✅ Ethanoic acid = CH₃COOH, –COOH group, acidic, pH ≈ 2.9–3.5, vinegar smell, boils at 117.9°C, freezes at 16.6°C ✅ Glacial acetic acid = pure ethanoic acid solidified at/below 16.6°C — looks like ice ✅ Blue litmus: ethanol = no change | ethanoic acid = turns RED ✅ Na₂CO₃ test: ethanol = no reaction | ethanoic acid = CO₂ fizzing (2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑) ✅ NaOH reaction: ethanol = no reaction | ethanoic acid = neutralisation (CH₃COOH + NaOH → CH₃COONa + H₂O) ✅ Esterification: ethanoic acid + ethanol + conc. H₂SO₄ + heat → sweet-smelling ethyl ethanoate ✅ Sodium metal test: BOTH react with Na giving H₂ — NOT a valid distinguishing test for this pair ✅ Root cause of all differences: –OH (neutral, no H⁺ release) vs –COOH (acidic, releases H⁺) ✅ Real life: ethanol = wine/sanitiser/biofuel | ethanoic acid = vinegar/food preservative/aspirin manufacturing

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