Class 10 Science – Pre-Board Mock Test Chapter: Carbon and Its Compounds

📝 Class 10 Science – Pre-Board Mock Test

Chapter: Carbon and Its Compounds
Maximum Marks: 40
Time: 2 Hours

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Section – A (1 × 5 = 5 marks)

1. Write the next homologue of butanol.
2. State two uses of ethanol.
3. Which property of carbon leads to the existence of a large number of organic compounds?
4. Why do ionic compounds conduct electricity in aqueous solution but not in solid state?
5. Write the molecular formula and structural formula of ethanoic acid.

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Section – B (2 × 5 = 10 marks)

6. Differentiate between covalent and ionic compounds (any two points).
7. Draw the electron dot structure of ethyne (C₂H₂).
8. Define denatured alcohol. Why is ethanol denatured?
9. Why are detergents more effective than soaps in hard water?
10. Write chemical equations for:
    (i) Reaction of CH₃COOH with NaHCO₃
    (ii) Oxidation of CH₃CH₂OH with acidified KMnO₄

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Section – C (3 × 5 = 15 marks)

11. Explain hydrogenation reaction. Write its equation and one industrial application.
12. (a) Define homologous series.
    (b) Write the molecular formula of 3 members of alkynes.
    (c) State any two characteristics of homologous series.
13. Explain the cleansing action of soap with a neat labeled diagram of micelle formation.
14. Give reasons:
    (i) Carbon forms strong covalent bonds.
    (ii) Carbon compounds generally have low melting and boiling points.
    (iii) Why are covalent compounds poor conductors of electricity?
15. Write chemical equations for the preparation of:
    (i) Ester (ethyl ethanoate)
    (ii) Saponification of ester
    (iii) Combustion of ethanol

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Section – D (5 × 2 = 10 marks)

16. An organic compound X has the molecular formula C₂H₆O.
    (a) Identify X and write its functional group.
    (b) Write the reaction when X is treated with:
    i) Sodium
    ii) Acidified KMnO₄
    (c) Write the reaction when X is heated with acetic acid in presence of concentrated H₂SO₄.
    (d) Name the sweet-smelling compound formed in the above reaction.

17. A compound ‘A’ (C₃H₆) reacts with H₂ in the presence of a catalyst to form compound ‘B’.
    (a) Identify A and B.
    (b) Name the type of reaction.
    (c) Write chemical equations involved.
    (d) What is the industrial application of this reaction?
    (e) Differentiate between addition and substitution reactions with one example each.

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✅ Suggested Marking Scheme / Answers

Section A (1 mark each)

1. Pentanol (C₅H₁₁OH)
2. Used as fuel, solvent, antiseptic, alcoholic beverages (any two).
3. Catenation.
4. In solid state ions not free, in aqueous solution ions are mobile.
5. CH₃COOH, structure:

H  O
 |  ||
H–C–C–OH
 |  
H

Section B (2 marks each)
6. Ionic: high m.p/b.p, conduct electricity in molten/aqueous state. Covalent: low m.p/b.p, poor conductors.
7. Ethyne (C₂H₂):

H–C≡C–H

8. Ethanol mixed with poisonous substances (methanol, pyridine) to prevent misuse for drinking.
9. Soaps form insoluble salts with Ca²⁺/Mg²⁺ (scum); detergents form soluble salts → effective in hard water.

(i) CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O
(ii) CH₃CH₂OH + [O] → CH₃COOH + H₂O

Section C (3 marks each)
11. Addition of H₂ to unsaturated hydrocarbon in presence of Ni catalyst. Example:
C₂H₄ + H₂ → C₂H₆
Industrial use: making vanaspati ghee.
12. (a) Series of compounds with same functional group/general formula.
(b) C₂H₂, C₃H₄, C₄H₆.
(c) Same chemical properties, differ by CH₂ unit.
13. Soap molecules form micelles. Hydrophobic tail traps oil/dirt, hydrophilic head in water → emulsification → dirt removed.
14. (i) Small size, high bond energy.
(ii) Weak intermolecular forces.
(iii) No free ions.
15. (i) CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O
(ii) CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
(iii) C₂H₅OH + O₂ → CO₂ + H₂O

Section D (5 marks each)
16. (a) X = Ethanol (C₂H₅OH), functional group = –OH.
(b) i) 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂
ii) C₂H₅OH + [O] → CH₃COOH + H₂O
(c) C₂H₅OH + CH₃COOH → CH₃COOC₂H₅ + H₂O
(d) Ester (ethyl ethanoate, sweet-smelling).

17. (a) A = Propene (C₃H₆), B = Propane (C₃H₈).
    (b) Hydrogenation (addition reaction).
    (c) C₃H₆ + H₂ → C₃H₈
    (d) Industrial use: hydrogenation of oils → vanaspati ghee.
    (e) Addition: H₂ adds to unsaturated compound (C₂H₄ + H₂ → C₂H₆).
    Substitution: one atom replaced (CH₄ + Cl₂ → CH₃Cl + HCl).

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📝 Answer Key – Class 10 Science (Carbon and Its Compounds Mock Test)

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Section A (1 mark each)

1. The next homologue of butanol is pentanol (C₅H₁₁OH).

2. Uses of ethanol:

• Used as fuel (biofuel, spirit).
• Used as solvent in medicines and perfumes.

3. The property of carbon is catenation – the ability to form bonds with other carbon atoms.

4. In solid state, ions are not free to move, so ionic compounds do not conduct electricity. In aqueous solution, ions become free and conduct electricity.

5. Ethanoic acid:

• Molecular formula: CH₃COOH
• Structural formula:

   H   O
   |   ||
H—C—C—OH
   |
   H

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Section B (2 marks each)

6. Difference between covalent and ionic compounds:

Covalent compounds	Ionic compounds
Low melting & boiling points	High melting & boiling points
Poor conductor of electricity	Good conductor when molten or dissolved in water

7. Electron dot structure of ethyne (C₂H₂):

H:C≡C:H

8. Denatured alcohol is ethanol mixed with poisonous substances like methanol to prevent misuse for drinking.
👉 Ethanol is denatured to avoid loss of revenue (excise duty) and prevent consumption.

9. Detergents are more effective than soaps in hard water because:

• Soaps form insoluble scum with calcium and magnesium salts in hard water.
• Detergents form soluble salts, hence clean better in hard water.

10.
(i) CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂ ↑
(ii) CH₃CH₂OH + [O] → CH₃COOH + H₂O

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Section C (3 marks each)

11. Hydrogenation reaction:
Addition of hydrogen to unsaturated hydrocarbons in the presence of catalyst (Ni/Pd/Pt).
Example:
C₂H₄ + H₂ → C₂H₆
Industrial application: Manufacture of vanaspati ghee from vegetable oils.

12.
(a) Homologous series – A series of organic compounds having the same functional group, same chemical properties, and successive members differ by –CH₂ group.
(b) Three members of alkyne: C₂H₂, C₃H₄, C₄H₆.
(c) Characteristics:

• Similar chemical properties.
• Gradation in physical properties.
• Same functional group.

13. Cleansing action of soap:

• Soap has hydrophobic tail (repels water) and hydrophilic head (attracts water).
• Dirt/oil is trapped inside micelle by hydrophobic tail.
• Micelles get suspended in water and wash away dirt.
  (Diagram of micelle with tails inside dirt droplet and heads outside in water required)

14. Reasons:
(i) Carbon forms strong covalent bonds because of small atomic size and strong C–C bond strength.
(ii) Carbon compounds have weak intermolecular forces, so they have low melting and boiling points.
(iii) Covalent compounds have no free ions, hence poor conductors of electricity.

15.
(i) Esterification: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O
(ii) Saponification: CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
(iii) Combustion: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

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Section D (5 marks each)

16. Compound X (C₂H₆O):

(a) X is ethanol (C₂H₅OH), functional group = –OH (alcohol).

(b) Reactions:
i) 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂ ↑
ii) C₂H₅OH + [O] → CH₃COOH + H₂O

(c) With acetic acid:
C₂H₅OH + CH₃COOH → CH₃COOC₂H₅ + H₂O

(d) The sweet-smelling compound formed is ethyl ethanoate (ester).

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17.

(a) A = Propene (C₃H₆), B = Propane (C₃H₈).

(b) Type of reaction: Hydrogenation (addition reaction).

(c) Equation: C₃H₆ + H₂ → C₃H₈

(d) Application: Hydrogenation of vegetable oils to make vanaspati ghee.

(e)

• Addition reaction: Unsaturated compound adds atoms.
  Example: C₂H₄ + H₂ → C₂H₆
• Substitution reaction: One atom replaces another.
  Example: CH₄ + Cl₂ → CH₃Cl + HCl

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