CG Board Class 10 Science Chapter 16 Solutions: Derivatives of Hydrocarbons (हाइड्रोकार्बन के व्युत्पन्न) (2026-27)

(i) When ethanol has 5% water added to it, it is called:**

• (a) Rectified spirit
• (b) Methylated spirit
• (c) Methanol
• (d) Absolute alcohol

(a) Rectified spirit

Explanation: Ethanol containing 5% water and 95% alcohol is known as rectified spirit.

Answer: (c) Teflon)

Explanation: Teflon (polytetrafluoroethylene) is chemically inert and withstands high corrosive pressure, so it is used for making packing gaskets and non-stick coatings.

Answer: (b) CO2

Explanation: Ethanoic acid reacts with carbonates to release carbon dioxide gas (CO₂) with brisk effervescence: 2CH_3COOH + Na_2CO₃ → 2CH_3COONa + H_2O + CO₂↑.

Answer: (a) Ethanoic acid

Explanation: Acetic acid (CH_3COOH) contains 2 carbon atoms, so its IUPAC name is Ethanoic acid.

(i) Ethanoic acid reacts with sodium**

(ii) Ethanol reacts with sodium

(i)

• (i) Ethanoic acid + Sodium: Sodium ethanoate (sodium acetate) salt is formed and hydrogen gas is released with effervescence

2CH_3COOH + 2Na → 2CH_3COONa + H₂↑

• (ii) Ethanol + Sodium: Sodium ethoxide salt is formed and hydrogen gas is released

2C_2H_5OH + 2Na → 2C_2H_5ONa + H₂↑

• (i) + :
• (ii) + :

(i) C_2H_5COOH + ? → (C_2H_5COO)_2Mg + H₂**

(ii) CH_3OH + CH_3COOH → [? ] ? + H_2O

(iii) CH_3COOH + Na_2CO₃ → ? + ? + CO₂

(i) C_2H_5COOH + ? → (C_2H_5COO)_2Mg + H₂

(ii) CH_3OH + CH_3COOH → [? ] ? + H_2O

(iii) CH_3COOH + Na_2CO₃ → ? + ? + CO₂

• (i) 2C_2H_5COOH + Mg → (C_2H_5COO)_2Mg + H₂↑
• (ii) CH_3OH + CH_3COOH → [H^+ / H_2SO₄] CH_3COOCH₃ + H_2O (Methyl ethanoate)
• (iii) 2CH_3COOH + Na_2CO₃ → 2CH_3COONa + H_2O + CO₂↑
• (i) 2C_2H_5COOH + Mg → (C_2H_5COO)_2Mg + H₂↑
• (ii) CH_3OH + CH_3COOH → [H^+ / H_2SO₄] CH_3COOCH₃ + H_2O
• (iii) 2CH_3COOH + Na_2CO₃ → 2CH_3COONa + H_2O + CO₂↑

Ethanol is used in low-temperature liquid thermometers because

1. It has a very low freezing point (-114°C), allowing measurement of extreme sub-zero cold temperatures where mercury freezes (-39°C).
2. It expands easily and uniformly with temperature rise.
3. Red dye can be easily added to colorless alcohol for clear scale readability.

Ethene is obtained by the dehydration of ethanol. When ethanol is heated at 443 K (170°C) with excess concentrated sulphuric acid (H_2SO₄), the acid acts as a dehydrating agent, removing a water molecule to form ethene

CH₃-CH₂-OH → [Conc. H_2SO₄ / 443 K] CH₂=CH₂ + H_2O

Structural isomers of Carboxylic Acids with molecular formula C_4H_8O₂

1. Butanoic acid: CH₃-CH₂-CH₂-COOH
2. 2-Methylpropanoic acid: CH₃-CH(CH₃)-COOH

(If considered for C_5H₁₀O₂):

1. Pentanoic acid: CH₃-CH₂-CH₂-CH₂-COOH
2. 2-Methylbutanoic acid: CH₃-CH₂-CH(CH₃)-COOH
3. 3-Methylbutanoic acid: CH₃-CH(CH₃)-CH₂-COOH
4. 2,2-Dimethylpropanoic acid: (CH₃)_3C-COOH

Industrial manufacture of ethanol is done by fermentation of molasses

1. Dilution: Molasses (syrup left after sugar crystallization) is diluted with water to an 8-10% solution.
2. Nutrients & Acidity: Ammonium sulphate ((NH₄)_2SO₄) is added as yeast food, and a little dilute H_2SO₄ is added to prevent bacterial infection.
3. Fermentation: 5% Yeast is added and the mixture is kept in an airtight tank at 25-30°C for 2-3 days.
4. Enzymatic Reactions:

• Invertase converts sucrose to glucose and fructose

C₁₂H₂₂O₁₁ + H_2O → [Invertase] C_6H₁₂O₆ + C_6H₁₂O₆

• Zymase ferments glucose/fructose into ethanol

C_6H₁₂O₆ → [Zymase] 2C_2H_5OH + 2CO₂↑

1. Fractional distillation yields 95% ethanol (rectified spirit).

Vinegar: A 3-4% dilute aqueous solution of ethanoic acid (acetic acid)** is called vinegar.

• Manufactured by Quick Vinegar Method:

1. A wooden tank with holes at the bottom for air circulation is filled with wood shavings soaked in old vinegar (containing Mycoderma aceti bacteria) and ammonium sulphate.
2. A 10% ethanol solution is trickled slowly from the top.
3. Acetobacter bacteria oxidize ethanol using atmospheric oxygen into ethanoic acid

C_2H_5OH + O₂ → [Mycoderma aceti] CH_3COOH + H_2O

1. Vinegar collects at the bottom of the tank.

Condensed Structure of PVC (Polyvinyl Chloride):**

-CH₂ – CH- | Cl _n

(Monomer: Vinyl chloride, CH₂=CHCl)

• Four Uses of PVC:

1. Insulation coating over electric wires and cables.
2. Manufacturing water drainage pipes and raincoats.
3. Making hand gloves, seat covers, and cycle mudguards.
4. Making toys and plastic sheets.

Reaction Name: Esterification Reaction**

• Odor Cause: Formation of an ester named Ethyl ethanoate (Ethyl acetate) which has a sweet, fruity smell.
• Balanced Equation:

CH_3COOH + C_2H_5OH → [Conc. H_2SO₄] CH_3COOC_2H₅ + H_2O

The evolved gas is Hydrogen gas (H₂), which burns with a ‘pop’ sound.

1. Reaction with Ethanol:

2C_2H_5OH + 2Na → 2C_2H_5ONa + H₂↑

(Sodium ethoxide + Hydrogen gas)

1. Reaction with Ethanoic Acid:

2CH_3COOH + 2Na → 2CH_3COONa + H₂↑

(Sodium ethanoate + Hydrogen gas)

Jaspreet can identify the liquids using either of these two simple chemical tests

1. Sodium Bicarbonate (NaHCO₃) Test: Add a pinch of baking soda (NaHCO₃) to a sample from both beakers

• The beaker which shows brisk effervescence with evolution of CO₂ gas contains Ethanoic acid.
• The beaker which shows no reaction contains Ethanol.

1. Litmus Paper Test:

• The liquid that turns blue litmus paper red is Ethanoic acid.
• The liquid that has no effect on litmus paper is Ethanol.

Polymer: A polymer is a high-molecular-mass macro-molecule formed by the repetitive chemical combination of hundreds or thousands of simple, low-molecular-mass repeating units called monomers**.

• Polymerization of Ethene: When a large number (n) of ethene (ethylene) monomer molecules (CH₂=CH₂) are heated under high pressure and temperature in the presence of a catalyst, the double bonds open up to form a long saturated chain macromolecule called Polythene

n(CH₂=CH₂) → [Catalytic Heat / Pressure] -CH₂ – CH₂– _n

1. Identification of Compound A:

• Molecular weight = 46 u.
• Formula for Ethanol (C_2H_5OH): (2 × 12) + (6 × 1) + 16 = 24 + 6 + 16 = 46 u.
• Ethanol is widely used as a sterilizing agent / antiseptic in medical fields.
• Therefore, Compound A = Ethanol (C_2H_5OH).

1. Identification of Compound B:

• Oxidation of ethanol yields Ethanoic acid (Acetic acid, CH_3COOH).
• Therefore, Compound B = Ethanoic acid (CH_3COOH).

1. Balanced Chemical Equation:

C_2H_5OH + 2[O] → [Alkaline KMnO₄ / K_2Cr_2O₇ + H^+] CH_3COOH + H_2O