Carbon and its Compounds | Class 10 CBSE | Web Notes | Part 4 - Some important Carbon Compounds

ETHANOL

Properties of Ethanol

• Ethanol is a liquid at room temperature.
• It is commonly called alcohol and is the active ingredient of all alcoholic drinks.
• It is a good solvent. So it is used in medicines such as tincture iodine, cough syrups, and tonics.
• Ethanol is soluble in water in all proportions.
• Consumption of small quantities of dilute ethanol causes drunkenness. Intake of even a small quantity of pure ethanol (absolute alcohol) is lethal. Long-term intake leads to many health problems.
• Ethanol for industrial use is made unfit for drinking by adding methanol. It is called denatured alcohol. Blue dyes are added to alcohol to identify it easily.
• Some countries use alcohol as an additive in petrol since it is a cleaner fuel. It releases only CO₂ and water.

Reactions of Ethanol

• a. Reaction with Sodium

Alcohols react with sodium, evolving hydrogen. E.g., Drop a small piece of sodium into pure ethanol. It produces sodium ethoxide (2CH₃CH₂O^–Na⁺) and H₂.

2Na + 2CH₃CH₂OH → 2CH₃CH₂O^–Na⁺ + H₂

• b. Reaction to Give Unsaturated Hydrocarbon

Heating ethanol at 443 K with excess concentrated H₂SO₄ results in dehydration of ethanol to give ethene. Concentrated H₂SO₄ is a dehydrating agent (removes water from ethanol).

ETHANOIC ACID

Properties of Ethanoic Acid (Acetic Acid)

• It belongs to carboxylic acids (weak acids).
• A 5-8% solution of acetic acid in water is called vinegar. It is used as a preservative in pickles.
• The melting point of pure ethanoic acid is 290 K, and hence it often freezes during winter. So it is known as glacial acetic acid.
• Acetic acid is a weak acid, while HCl is a strong acid.

Reactions of Ethanoic Acid

a. Esterification Reaction

• It is the formation of esters by the reaction of an acid and an alcohol.
• E.g., Take 1 mL absolute ethanol + 1 mL glacial acetic acid + a few drops of concentrated H₂SO₄ in a test tube.
• Warm in a water bath for 5 minutes.

• Pour into a beaker containing 20-50 mL of water. The resulting mixture is an ester.
• Here, ethanoic acid reacts with ethanol in the presence of an acid catalyst to give an ester.
• Esters have a sweet smell.
• Uses of esters: To make perfumes and as flavouring agents.
• On treating with NaOH (an alkali), the ester is converted back to alcohol and the sodium salt of carboxylic acid. This reaction is called saponification because it is used in the preparation of soap.

b. Reaction with a Base

Ethanoic acid reacts with a base like NaOH to give a salt (sodium ethanoate or sodium acetate) and water.

NaOH + CH₃COOH → CH₃COONa + H₂O

c. Reaction with Carbonates & Hydrogen Carbonates

Take a spatula full of sodium carbonate in a test tube and add 2 mL dilute ethanoic acid. The following reaction occurs:

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ + H₂O
                      (Sodium acetate)

Pass the gas produced through lime-water. Lime-water turns milky, indicating that the gas is CO₂.

Reaction with sodium hydrogen carbonate:

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Select a Topic 👇

1. Bonding in Carbon - the Covalent Bond 2. Versatile Nature of Carbon 3. Chemical properties of Carbon Compounds 4. Some important Carbon Compounds 5. Soaps and Detergents

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