CBSE Class 10 - Carbon and its Compounds Notes & MCQ

January 05, 2026

Carbon and its Compounds

Carbon and its Compounds

1. Bonding in Carbon – The Covalent Bond

  • Atomic number of carbon = 6
  • Electronic configuration → 2, 4 (4 valence electrons)
  • Carbon cannot form ionic bonds easily (losing/gaining 4 electrons requires huge energy)
  • Carbon forms covalent bonds by sharing electrons → achieves noble gas configuration
  • Covalent compounds have:
    • Low melting & boiling points
    • Poor conductors of electricity (no free ions/electrons)
    • Usually insoluble in water (except few like alcohols)

Electron dot structure examples:

  • Methane (CH₄): Carbon shares 4 electrons with 4 H atoms
  • Ethene (C₂H₄): Double bond between two C atoms
  • Ethyne (C₂H₂): Triple bond between two C atoms

2. Versatile Nature of Carbon

Carbon forms more than 3 million compounds → due to two unique properties:

  • Tetravalency: Carbon has 4 valence electrons → can form 4 covalent bonds
  • Catenation: Ability to form long chains, branches & rings by bonding with other carbon atoms (C–C bond is very strong & stable)

Other reasons: Small size of carbon atom, Ability to form single, double & triple bonds.

Allotropes of Carbon:

Image of the structure of diamond, graphite, and buckminsterfullerene

  • Diamond: Hardest natural substance, bad conductor, used in cutting tools & jewellery
  • Graphite: Soft, slippery, good conductor (used in pencils & electrodes)
  • Fullerenes: e.g., Buckminsterfullerene (C₆₀) – football-shaped
  • Graphene: Single layer of graphite (very strong & conductor)

3. Saturated and Unsaturated Carbon Compounds (Hydrocarbons)

Type Bonds General Formula Example Reactivity
Saturated Only single C–C bonds CₙH₂ₙ₊₂ Methane (CH₄), Ethane (C₂H₆) Less reactive
Unsaturated At least one double/triple bond — — More reactive
  • Alkanes (saturated): CₙH₂ₙ₊₂ (e.g., CH₄, C₂H₆, C₃H₈)
  • Alkenes (unsaturated, one double bond): CₙH₂ₙ (e.g., Ethene C₂H₄)
  • Alkynes (unsaturated, one triple bond): CₙH₂ₙ₋₂ (e.g., Ethyne C₂H₂)

4. Chains, Branches and Rings

  • Straight chain: e.g., n-Pentane (C₅H₁₂)
  • Branched chain: e.g., Isopentane, Neopentane (isomers)
  • Ring (cyclic): e.g., Cyclohexane (C₆H₁₂), Benzene (C₆H₆ – aromatic)

5. Homologous Series

A series of organic compounds having the same functional group and similar chemical properties, but successive members differ by –CH₂– unit (14 u in molecular mass).

Characteristics: Same general formula, similar chemical properties, gradual change in physical properties (boiling point increases with chain length).

Example: Alcohols: CH₃OH (Methanol) → C₂H₅OH (Ethanol) → C₃H₇OH (Propanol) ...

6. Functional Groups & Nomenclature (IUPAC)

Functional Group Formula Suffix/Prefix Example
Alkane — –ane Methane
Alkene C=C –ene Ethene
Alkyne C≡C –yne Ethyne
Alcohol –OH –ol Ethanol (C₂H₅OH)
Aldehyde –CHO –al Ethanal (CH₃CHO)
Ketone >C=O –one Propanone (CH₃COCH₃)
Carboxylic acid –COOH –oic acid Ethanoic acid (CH₃COOH)
Halogen –X (Cl,Br,I) Prefix: chloro/bromo Chloromethane (CH₃Cl)

7. Chemical Properties of Carbon Compounds

  • Combustion: CH₄ + 2O₂ → CO₂ + 2H₂O + heat & light
  • Oxidation: Ethanol → Ethanoic acid (using alkaline KMnO₄)
  • Addition reaction: Ethene + H₂ → Ethane (Ni catalyst, heat) - used in hydrogenation of oils
  • Substitution reaction: CH₄ + Cl₂ → CH₃Cl + HCl (in sunlight)

8. Some Important Carbon Compounds

A. Ethanol (C₂H₅OH)

Colourless, pleasant smell, volatile liquid. Reactions include combustion, reaction with Na (H₂ gas), and dehydration to Ethene.

B. Ethanoic acid (CH₃COOH)

Sour taste, turns blue litmus red. 5-8% solution is Vinegar. Reactions include esterification and reaction with NaHCO₃ (CO₂ effervescence).

9. Soaps and Detergents

Image of soap micelle structure

  • Soap: Sodium/potassium salt of long-chain fatty acids.
  • Structure: Hydrophilic head (water loving) and Hydrophobic tail (oil loving).
  • Cleansing: Micelle formation emulsifies dirt.
Feature Soap Detergent
Source Natural (fats/oils) Synthetic (petroleum)
In hard water Forms scum No scum
Biodegradability Biodegradable Some are non-biodegradable

MCQs: Carbon and its Compounds

  1. Which of the following is the correct electronic configuration of carbon?
    1. 2, 8
    2. 2, 4
    3. 2, 6
    4. 2, 8, 2
    Ans: B) 2, 4
  2. The property of carbon atoms due to which they can form long chains and rings is called:
    1. Tetravalency
    2. Catenation
    3. Isomerism
    4. Allotropy
    Ans: B) Catenation
  3. Which of the following is an unsaturated hydrocarbon?
    1. Ethane
    2. Propane
    3. Ethene
    4. Butane
    Ans: C) Ethene
  4. The general formula of alkynes is:
    1. CₙH₂ₙ₊₂
    2. CₙH₂ₙ
    3. CₙH₂ₙ–2
    4. CₙHₙ
    Ans: C) CₙH₂ₙ–2
  5. Which functional group is present in ethanol?
    1. –CHO
    2. –COOH
    3. –OH
    4. >C=O
    Ans: C) –OH
  6. The compound formed when ethanol reacts with sodium metal is:
    1. Sodium ethoxide + Hydrogen
    2. Sodium acetate + Hydrogen
    3. Ethene + Hydrogen
    4. Ethanoic acid + Sodium
    Ans: A) Sodium ethoxide + Hydrogen
  7. Which of the following reactions is shown only by unsaturated hydrocarbons?
    1. Substitution reaction
    2. Addition reaction
    3. Combustion reaction
    4. Oxidation reaction
    Ans: B) Addition reaction
  8. The catalyst used in hydrogenation of vegetable oils is:
    1. Fe
    2. Ni
    3. Pt
    4. Pd
    Ans: B) Ni
  9. Which allotrope of carbon is used as a lubricant?
    1. Diamond
    2. Graphite
    3. Fullerene
    4. Coke
    Ans: B) Graphite
  10. The IUPAC name of CH₃–CH=CH–CH₃ is:
    1. Butane
    2. Butene
    3. But-2-ene
    4. But-1-ene
    Ans: C) But-2-ene
  11. Which of the following compounds is formed when ethanoic acid reacts with ethanol in presence of conc. H₂SO₄?
    1. Ethyl ethanoate
    2. Ethene
    3. Methane
    4. Sodium ethanoate
    Ans: A) Ethyl ethanoate
  12. The gas evolved when ethanoic acid reacts with sodium bicarbonate is:
    1. Hydrogen
    2. Oxygen
    3. Carbon dioxide
    4. Nitrogen
    Ans: C) Carbon dioxide
  13. Which of these will form scum when used with hard water?
    1. Detergent
    2. Soap
    3. Both soap and detergent
    4. Neither soap nor detergent
    Ans: B) Soap
  14. The structural formula of a compound having molecular formula C₄H₁₀ is:
    1. CH₃–CH₂–CH=CH₂
    2. CH₃–CH₂–CH₂–CH₃
    3. CH₃–C≡C–CH₃
    4. CH₂=CH–CH₂–CH₃
    Ans: B) CH₃–CH₂–CH₂–CH₃
  15. Which of the following is a homologous series?
    1. CH₄, C₂H₄, C₃H₆
    2. CH₃OH, C₂H₅OH, C₃H₇OH
    3. CH₃Cl, C₂H₅Cl, C₃H₇Cl
    4. Both B and C
    Ans: D) Both B and C
  16. The product formed on complete oxidation of ethanol is:
    1. Ethene
    2. Ethanoic acid
    3. Methane
    4. Carbon monoxide
    Ans: B) Ethanoic acid
  17. Buckminsterfullerene is an allotrope of carbon having the formula:
    1. C₆
    2. C₆₀
    3. C₇₀
    4. C₁₂
    Ans: B) C₆₀
  18. Which type of reaction is: CH₄ + Cl₂ → CH₃Cl + HCl (in sunlight)?
    1. Addition
    2. Substitution
    3. Esterification
    4. Oxidation
    Ans: B) Substitution
  19. The micelle formation in soap solution helps in:
    1. Making water soft
    2. Removing dirt and grease
    3. Increasing boiling point
    4. Decreasing surface tension only
    Ans: B) Removing dirt and grease
  20. Which of the following compounds has a –COOH functional group?
    1. Methanol
    2. Ethanal
    3. Methanoic acid
    4. Propanone
    Ans: C) Methanoic acid

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