🧪 UNIT – 4 : CARBON AND ITS COMPOUNDS(Question)

 

🧪 UNIT – 4 : CARBON AND ITS COMPOUNDS

Learning Points

• Bonding in carbon – the covalent bond

• Versatile nature of carbon

• Saturated and unsaturated carbon compounds

• Chains, branches, and rings

• Functional groups

• Homologous series

• Nomenclature of carbon compounds

• Combustion, oxidation, addition and substitution reactions

• Properties of ethanol and ethanoic acid

• Soaps and detergents

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I. Multiple Choice Questions (1 Mark each)

1. The valence electrons that an atom of carbon has in its outermost shell are
   A. 1 B. 2 C. 3 D. 4

2. Diatomic molecule produced by the formation of double bond is
   A. Chlorine B. Oxygen C. Nitrogen D. Ammonia

3. The major component of biogas is
   A. Propane B. Butane C. Methane D. Ethane

4. Carbon can form bonds with other carbon atoms giving rise to large molecules. This property is called
   A. Saponification B. Catenation C. Hydrogenation D. Esterification

5. An unsaturated compound in which double bond is found between carbon atoms is
   A. Methane B. Ethane C. Ethene D. Ethyne

6. Functional group found in haloalkanes is
   A. −Cl or −Br B. −OH C. −CHO D. −COOH

7. The structural formula of propanal is ______

8. The name of the compound shown in figure is
   A. Propanone B. Propanol C. Propanal D. Propanoic acid

9. The number of single and double bonds present in benzene are respectively
   A. 6 and 6 B. 9 and 3 C. 7 and 5 D. 3 and 9

10. The number of single bonds present in the structure of cyclohexane is
    A. 12 B. 18 C. 24 D. 6

11. The number of carbon and hydrogen atoms in the fifth member of alkene series is
    A. Five and ten B. Five and twelve C. Six and twelve D. Six and six

12. The molecular formula of both cyclohexane and hexane is
    A. C₆H₁₂ B. C₆H₁₄ C. C₆H₁₀ D. C₆H₆

13. Difference between molecular formulae of two successive homologous compounds is
    A. CH₂ B. CH₄ C. C₂H₂ D. C₂H₄

14. The group of compounds forming a homologous series is
    A. CH₄, C₂H₄, C₂H₂ B. CH₄, CH₃OH, HCHO
    C. C₂H₂, C₂H₆, CH₄ D. C₂H₂, C₃H₄, C₄H₆

15. The correct group of saturated hydrocarbons is
    A. Methane, Ethene, Ethyne B. Ethane, Propane, Butane
    C. Ethyne, Ethane, Methane D. Ethyne, Propene, Butyne

16. General formula of alkynes is
    A. CnH₂n–2 B. CnH₂n+2 C. CnH₂n D. CnH₂n+1

17. The molecular formula of three compounds in a homologous series is C₂H₆, C₃H₈, C₄H₁₀. The general formula is
    A. CnH₂n B. CnH₂n–1 C. CnH₂n–2 D. CnH₂n+2

18. Organic compounds formed by the reaction of carboxylic acid and alcohol are
    A. Aldehydes B. Ketones C. Esters D. Haloalkanes

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II. One Mark Questions

19. Write the electron dot structure of methane.

20. Mention the number of single and double bonds in C₂H₅COOH.

21. Write the structural formula of ethene.

22. Name the given organic compounds.

23. Write the structural formula of the ketone having three carbon atoms.

24. If the first member of an alkene has formula C₂H₄, find the formula of the fifth member.

25. Write the molecular and structural formula of benzene.

26. Why are hydrocarbons used as fuels?

27. Give reason: Why is addition reaction used in hydrogenation of vegetable oils?

28. Why is ethanoic acid called glacial acetic acid?

29. The 5–8% solution of acetic acid in water is called ______.

30. When ethanol reacts with sodium, which gas evolves and how is it tested?

31. Name the compound produced when ethanoic acid reacts with a base.

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III. Two Mark Questions

32. Give reason:
    a) Covalent compounds have low melting and boiling points.
    b) Covalent compounds are poor conductors of electricity.

33. Write two important factors observed in carbon.

34. Give reason:
    a) As molecular mass increases in a homologous series, a gradation in physical properties is seen.
    b) Functional group determines chemical properties which remain similar.

35. Write electron dot structures for:
    i) Hydrogen ii) Ethane.

36. What are functional groups? Name the functional groups in propanal and propanol.

37. What are functional groups? Write the structural formula of the compound obtained when one H atom in ethane is replaced by –CHO group.

38. In a group of unsaturated hydrocarbons, though C:H ratio is 1:2, CH₂ is not the first member. Why? Write the structural formula of the first member.

39. The first member of a series has CH₂O (HCHO). Find the third member and general name for this group.

40. CH₄ + Cl₂ → CH₃Cl + HCl (sunlight). Identify the reaction and justify.

41. What are alkynes? Name the first member and write its molecular formula.

42. Complete the following reaction and explain why it is called saponification:
     CH₃COOC₂H₅ + NaOH → C₂H₅OH + ______

43. Observe the given reactions and name the products ‘a’ and ‘b’. Identify which are saturated and unsaturated.

44. Name the carbon compounds of the given structures.

45. Write an activity to show formation of ester. How can it be detected?

46. Explain the reaction of ethanoic acid with sodium carbonate and sodium hydrogen carbonate using balanced equations.

47. What is esterification? Mention uses of esters.

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IV. Three Mark Questions

48. a) What is the property of carbon that allows it to form large number of compounds?
    b) Why is this property seen to a great extent in carbon?
    c) Name the arrangements of carbon atoms in such compounds.

49. a) What are saturated carbon compounds?
    b) Define:
     i) Homologous series ii) Esters.

50. a) What are micelles?
    b) What is a covalent bond? Write any two properties of covalent compounds.

51. a) What are substitution reactions?
    b) Name the simplest hydrocarbon and write its formula.
    c) What are oxidising agents?

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V. Four Mark Questions

52. a) Explain why conversion of ethanol to ethanoic acid is an oxidation reaction.
    b) Write characteristics of acetic acid.

53. What are structural isomers? Write structural isomers of butane.

54. a) Explain the cleaning action of soaps.
    b) Which salts cause hardness of water? Why are detergents effective in hard water?

55. a) Why can carbon not form C⁴⁺ or C⁴⁻ ions?
    b) Write the electron dot structures of N₂ and C₂H₄ molecules.

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VI. Five Mark Question

56. a) Write any two differences between saturated and unsaturated carbon compounds.
    b) Write molecular and structural formulae for:
     i) Propanoic acid ii) Cyclohexane iii) Pentane.

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I. Multiple Choice Questions – 1 Mark each

No.	Question (brief)	Correct Answer
1	Valence electrons of carbon	D. 4
2	Diatomic molecule with double bond	B. Oxygen
3	Major component of biogas	C. Methane
4	Property forming large molecules	B. Catenation
5	Unsaturated compound with double bond	C. Ethene
6	Functional group in haloalkanes	A. −Cl or −Br
7	Structural formula of propanal	(CH₃CH₂CHO)
8	Name of given compound	A. Propanone
9	Bonds in benzene	B. 9 single and 3 double
10	Single bonds in cyclohexane	B. 18
11	Atoms in 5th alkene	C. Six C and twelve H
12	Molecular formula of cyclohexane	A. C₆H₁₂
13	Difference in homologous series	A. CH₂
14	Compounds in homologous series	D. C₂H₂, C₃H₄, C₄H₆
15	Group of saturated hydrocarbons	B. Ethane, Propane, Butane
16	General formula of alkyne	A. CnH₂n–2
17	General formula of C₂H₆, C₃H₈, C₄H₁₀	D. CnH₂n+2
18	Product of acid + alcohol	C. Esters

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II. One Mark Answers

19. Methane electron-dot structure:
    Central carbon shares four pairs of electrons with four H atoms (CH₄).

20. Bonds in C₂H₅COOH:
    9 single bonds, 1 double bond.

21. Ethene structure:
    H₂C=CH₂.

22. Methanal (HCHO) and Bromoethane (C₂H₅Br).

23. Ketone with 3 carbons: Propanone (CH₃COCH₃).

24. Fifth member of alkene (C₂H₄ first): C₆H₁₂.

25. Benzene formula: C₆H₆, structural: ring of alternating double bonds.

26. Hydrocarbon fuels reason:
    Combustion releases large heat & light.

27. Addition reaction in hydrogenation:
    Converts unsaturated → saturated oils.

28. Glacial acetic acid:
    Pure ethanoic acid freezes at 290 K.

29. 5–8% acetic acid solution: Vinegar.

30. Gas evolved from ethanol + Na: Hydrogen gas; burns with pop sound.

31. Ethanoic acid + base:
    NaOH + CH₃COOH → CH₃COONa + H₂O.

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III. Two Mark Answers

32. Covalent compounds:
    a) Low melting/boiling → weak forces.
    b) Poor conductors → no free ions.

33. Carbon’s special factors:
    i) Catenation. ii) Tetravalency.

34. Homologous series properties:
    a) Gradation with molecular mass.
    b) Similar chemical behaviour due to same functional group.

35. Electron-dot structures:
    i) Hydrogen – H:H ii) Ethane – H₃C–CH₃.

36. Functional groups:
    Group of atoms conferring properties; propanal (–CHO), propanol (–OH).

37. Functional group example:
    Replace H in ethane with –CHO → CH₃CHO (Ethanal).

38. Reason CH₂ not first in alkene:
    Carbon cannot form double bond with H; first is C₂H₄.

39. Homologous series example:
    CH₂O (formaldehyde), next – CH₃CHO (acetaldehyde), third – C₂H₅CHO (propionaldehyde).

40. CH₄ + Cl₂ → CH₃Cl + HCl:
    Substitution reaction – Cl replaces H.

41. Alkynes:
    Unsaturated hydrocarbons with triple bond.
    First member: Ethyne (C₂H₂).

42. Saponification:
    CH₃COOC₂H₅ + NaOH → C₂H₅OH + CH₃COONa.
    Used in soap making.

43. ‘a’ and ‘b’ reactions:
    a – Ethene (unsaturated), b – Ethane (saturated).

44. Name of compounds:
    i) Propanoic acid ii) Butene iii) Ethanol iv) Pentyne.

45. Ester formation activity:
    Heat ethanol + acetic acid + conc. H₂SO₄ → fruity ester. Detect by sweet smell.

46. Ethanoic acid reactions:
    2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
    CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

47. Esterification reaction:
    Acid + Alcohol → Ester + Water.
    Uses: Perfumes, flavouring agents.

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IV. Three Mark Answers

48. Versatility of carbon:
    a) Property – Catenation.
    b) Reason – strong C–C bonds.
    c) Forms: long chain, branched, ring structures.

49. a) Saturated – single C–C bonds.
    b) i) Homologous series – differ by CH₂ unit.
     ii) Esters – sweet-smelling products of acid + alcohol.

50. a) Micelles – soap molecules with hydrophilic and hydrophobic ends.
    b) Covalent bond – shared electron pair.
    Covalent compounds: low m.p/b.p, poor conductors.

51. a) Substitution reaction – H replaced by another atom/group.
    b) Simplest hydrocarbon – Methane (CH₄).
    c) Oxidising agents – add oxygen (e.g., KMnO₄).

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V. Four Mark Answers

52. (a) Ethanol → Ethanoic acid (adds oxygen → oxidation).
    (b) Acetic acid properties – weak organic acid, mp 290 K, group: carboxylic acid.

53. Structural isomers:
    Same molecular, different structural formula.
    Example: Butane →

• n-butane: CH₃–CH₂–CH₂–CH₃

• isobutane: (CH₃)₂CH–CH₃

54. (a) Soap action: Micelles form around grease → emulsify → wash away.
    (b) Hard water salts – Ca²⁺, Mg²⁺. Detergents work in hard water (no precipitate).

55. (a) Carbon cannot form C⁴⁺ or C⁴⁻ – energy too high.
    (b) Electron-dot structures:
    N₂ : N≡N  Ethene : H₂C=CH₂.

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VI. Five Mark Answers

56. (a) Saturated vs Unsaturated compounds:

Saturated	Unsaturated
Single C–C bond	Double/triple C–C bond
Less reactive	More reactive
Substitution reactions	Addition & substitution
Blue flame	Yellow flame

(b) Molecular & structural formulas:

1. Propanoic acid – C₂H₅COOH

2. Cyclohexane – C₆H₁₂

3. Pentane – C₅H₁₂