💎 Carbon and Its Compounds: Comprehensive Class 10 Notes

📑 In This Chapter Guide (Table of Contents)

1. 1. Why Does Carbon Form Covalent Bonds?
2. 2. Homologous Series & Functional Groups
3. 3. Important Chemical Reactions of Carbon Compounds
4. 4. Soaps, Detergents and Micelle Cleansing Mechanism
5. 💡 Frequently Asked Questions (FAQ)

1. Why Does Carbon Form Covalent Bonds?

Carbon has atomic number 6 with electronic configuration (2,4). To achieve noble gas neon configuration, carbon needs 4 electrons. However:

• It cannot gain 4 electrons to form C⁴⁻ because a nucleus with only 6 protons cannot stably hold 10 electrons.
• It cannot lose 4 electrons to form C⁴⁺ because removing 4 electrons requires massive ionization energy.

Therefore, carbon overcomes this limitation by sharing valence electrons with other atoms, forming stable Covalent Bonds.

The Versatile Nature of Carbon (Why Millions of Compounds Exist):

• Catenation: Unique ability of carbon atoms to form strong, stable covalent bonds with other carbon atoms, creating long open chains, branched chains, or closed rings.
• Tetravalency: Having a valency of 4, a carbon atom can bond with four other monovalent atoms (H, Cl) or polyvalent atoms (O, N, S).
• Small Atomic Size: Enables the nucleus to hold the shared electron pairs firmly, giving carbon-carbon bonds immense thermal and chemical stability.

2. Homologous Series & Functional Groups

A Homologous Series is a family of organic compounds having the same functional group and similar chemical properties, in which successive members differ by a -CH₂- unit (and 14 atomic mass units in molecular weight).

Key Functional Groups in Class 10:

• Alcohol (-OH): Suffix -ol. E.g., Methanol (CH₃OH), Ethanol (C₂H₅OH).
• Aldehyde (-CHO): Suffix -al. E.g., Methanal (HCHO), Ethanal (CH₃CHO).
• Ketone (-CO-): Suffix -one. Carbonyl group must be non-terminal. Smallest ketone is Propanone (Acetone, CH₃COCH₃).
• Carboxylic Acid (-COOH): Suffix -oic acid. E.g., Methanoic acid (HCOOH), Ethanoic acid (Acetic acid, CH₃COOH).
• Haloalkanes (-Cl, -Br): Prefix Chloro- or Bromo-. E.g., Chloromethane (CH₃Cl).

3. Important Chemical Reactions of Carbon Compounds

Master these 5 core organic reactions for board examinations:

• Combustion: Complete burning in oxygen yields CO₂, water vapor, heat, and light:
  CH₄ + 2O₂ → CO₂ + 2H₂O + Heat + Light
• Oxidation: Alcohols are oxidized to carboxylic acids using Alkaline Potassium Permanganate (KMnO₄) or Acidified Potassium Dichromate (K₂Cr₂O₇):
  CH₃CH₂OH --[Alk. KMnO₄ + Heat]--> CH₃COOH
• Addition Reaction: Unsaturated hydrocarbons (alkenes/alkynes) add hydrogen in the presence of Nickel or Palladium catalyst to form saturated alkanes (Industrial hydrogenation of vegetable oils into vanaspati ghee):
  R₂C=CR₂ + H₂ --[Ni catalyst]--> R₂CH-CHR₂
• Substitution Reaction: In the presence of sunlight, chlorine displaces hydrogen atoms from alkanes one by one:
  CH₄ + Cl₂ --[Sunlight]--> CH₃Cl + HCl
• Esterification & Saponification:
  • Esterification: Ethanoic acid reacts with absolute ethanol in the presence of concentrated H₂SO₄ to form a sweet-smelling ester (Ethyl Ethanoate):
    CH₃COOH + C₂H₅OH --[Conc. H₂SO₄]--> CH₃COOC₂H₅ + H₂O
  • Saponification: Alkaline hydrolysis of esters with sodium hydroxide yields soap and alcohol:
    CH₃COOC₂H₅ + NaOH → CH₃COONa [Sodium Acetate Soap] + C₂H₅OH

4. Soaps, Detergents and Micelle Cleansing Mechanism

A soap molecule consists of two chemically distinct parts:

• Ionic Hydrophilic Head (-COO⁻Na⁺): Water-loving, interacts with polar water molecules and points outward.
• Hydrocarbon Hydrophobic Tail: Oil-loving / water-hating, interacts with grease, dirt, and oils and points inward.

Micelle Formation: In aqueous solution, soap molecules cluster radially around greasy dirt droplets. The hydrophobic tails dissolve in the oil droplet at the center, while ionic heads remain exposed to water on the spherical periphery. This forms an emulsion called a Micelle. Agitation pulls the grease off fabric into the wash water.

Why Detergents Outperform Soaps in Hard Water: Hard water contains Calcium (Ca²⁺) and Magnesium (Mg²⁺) salts. Soap reacts with these ions to form an insoluble sticky white precipitate called Scum, wasting soap. Synthetic detergents (sodium salts of sulphonic acids) do not form insoluble precipitates with Ca²⁺ and Mg²⁺, working effectively in both soft and hard water.

💡 Frequently Asked Questions (FAQ)

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