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CA06 — Organic & Everyday Chemistry

✈ Chemistry – CA06  ·  AFCAT General Awareness AFCAT Level ★ High Priority

Carbon forms more compounds than all other elements combined. This chapter covers organic chemistry basics — allotropes of carbon, hydrocarbons, functional groups — plus the chemistry behind everyday products you use. AFCAT asks about soaps, polymers, fertilisers and glass directly.

📌 AFCAT Focus: Allotropes (diamond = hardest; graphite = conductor); hydrocarbon formula series (CₙH₂ₙ₊₂ for alkanes); ethanol uses; saponification = how soap is made; Nylon = condensation polymer; Teflon = addition polymer from tetrafluoroethene; urea = nitrogen fertiliser.
PART 1 — CARBON: ALLOTROPES & HYDROCARBONS

1. Allotropes of Carbon & Hydrocarbons

Fig. 1 — Carbon Allotropes and Hydrocarbon Homologous Series
CARBON: ALLOTROPES (Top) and HYDROCARBONS (Bottom) DIAMOND Hardest natural substance Each C bonds to 4 C atoms. 3D rigid tetrahedral network. No free electrons → insulator. Uses: cutting tools, jewellery. Mohs hardness = 10 (maximum) GRAPHITE Only non-metal conductor! Each C bonds to 3 C atoms. Hexagonal layers; slide freely. 1 free e⁻ per C → conducts. Uses: pencils, electrodes, lubricant. Mohs hardness = 1–2 (very soft) FULLERENE (C₆₀) Buckminsterfullerene 60 C atoms in soccer-ball cage. 20 hexagons + 12 pentagons. Hollow structure. Uses: drug delivery, nanotechnology. Nobel Prize 1996 (Curl, Kroto, Smalley) HYDROCARBON HOMOLOGOUS SERIES — General Formulae Series Formula Bond type Example (n=2) Use ALKANES CₙH₂ₙ₊₂ Single bond only Saturated Ethane C₂H₆ LPG, CNG fuel ALKENES CₙH₂ₙ One C=C double bond Unsaturated Ethene C₂H₄ Polyethylene; fruit ripening
PART 2 — EVERYDAY CHEMISTRY

2. Soaps, Polymers & Industrial Compounds

Soap Making (Saponification):

Fat/Oil (triglyceride) + NaOH (caustic soda) → Soap (sodium salt of fatty acid) + Glycerol
● NaOH → hard soap (bar soap)    |    KOH → soft soap (shaving cream, liquid soap)
● Micelle formation: Non-polar tail of soap dissolves in grease; polar head faces water → dirt removed
● Detergents work in hard water (soap scum forms in hard water; detergents do not)
⚠ Why Detergents Work in Hard Water (Soap Does NOT) — Direct AFCAT Question:

Hard water contains dissolved Ca²⁺ and Mg²⁺ ions. When soap (sodium stearate) meets hard water, these ions react with the fatty acid part of soap to form calcium/magnesium stearate — an insoluble white scum. This wastes soap and leaves a grey residue on fabric.

Detergents contain a sulphonate (—SO₃⁻) or sulphate (—OSO₃⁻) group instead of carboxylate (—COO⁻). Calcium and magnesium salts of these groups are soluble in water, so no scum forms. Detergents clean effectively even in hard or sea water.
Summary:
Soap (—COO⁻) + Ca²⁺ → insoluble scum → does NOT work in hard water.
Detergent (—SO₃⁻) + Ca²⁺ → soluble salt → works in hard water.
PolymerMonomerTypeKey Use PolyethyleneEthene (C₂H₄)AdditionPlastic bags, bottles, films PVCVinyl chloride (CH₂=CHCl)AdditionPipes, cables, flooring Teflon (PTFE)Tetrafluoroethene (C₂F₄)AdditionNon-stick cookware, seals Nylon-6,6Hexamethylenediamine + Adipic acidCondensationRopes, parachutes, toothbrush PolyesterEthylene glycol + Terephthalic acidCondensationClothing, PET bottles BakelitePhenol + FormaldehydeCondensationElectrical switches, handles

3. Glass, Cement & Fertilisers

SubstanceComposition / Key FactUse Soda GlassSiO₂ + Na₂CO₃ + CaCO₃ (fused)Windows, bottles, common glassware Borosilicate glass (Pyrex)SiO₂ + B₂O₃ (boron trioxide)Lab glassware; heat-resistant cookware Portland CementCaO + SiO₂ + Al₂O₃ + Fe₂O₃Construction (concrete = cement+sand+gravel) UreaCO(NH₂)₂ — 46% nitrogenMost common nitrogen fertiliser SuperphosphateCa(H₂PO₄)₂ — phosphorus sourcePhosphorus (P) fertiliser for root growth Muriate of PotashKCl — potassium sourcePotassium (K) fertiliser; disease resistance

📝 AFCAT PYQs — Organic & Everyday Chemistry

Q1. Diamond is harder than graphite because: AFCAT PYQ
(a) Diamond has more carbon atoms(b) Diamond has a rigid 3D covalent lattice(c) Graphite has metallic bonding(d) Diamond is denser
✔ Answer: (b) Rigid 3D covalent lattice
In diamond, each carbon is covalently bonded to four others in a rigid 3D tetrahedral network — the strongest possible bonding arrangement. There are no free electrons or weak forces. In graphite, carbon layers are held together only by weak van der Waals forces and can slide easily (making graphite soft and a lubricant). Both are pure carbon — structure determines properties.
Q2. The process of making soap from oil and caustic soda is called: AFCAT PYQ
(a) Hydrogenation(b) Saponification(c) Esterification(d) Polymerisation
✔ Answer: (b) Saponification
Saponification: Fat/Oil + NaOH → Soap + Glycerol. This is the chemical reaction used to make soap. NaOH (caustic soda) gives hard bar soap; KOH gives soft/liquid soap. The resulting soap molecule has a non-polar tail (dissolves in grease) and a polar head (dissolves in water) — forming micelles that lift dirt away.
Q3. Which fertiliser has the highest nitrogen content? AFCAT PYQ
(a) Ammonium sulphate(b) Calcium nitrate(c) Urea(d) Superphosphate
✔ Answer: (c) Urea
Urea CO(NH₂)₂ has 46% nitrogen content — the highest nitrogen percentage among all solid fertilisers. This is why it is the most widely used nitrogen fertiliser globally. Ammonium sulphate has ~21% N; calcium nitrate ~15% N. Superphosphate provides phosphorus (P), not nitrogen. The NPK (Nitrogen-Phosphorus-Potassium) distinction is directly tested in AFCAT.
Q4. Teflon is made by polymerisation of: AFCAT PYQ
(a) Ethene(b) Vinyl chloride(c) Tetrafluoroethene(d) Styrene
✔ Answer: (c) Tetrafluoroethene
Teflon (PTFE — polytetrafluoroethylene) is made by addition polymerisation of tetrafluoroethene (C₂F₄). The strong C—F bonds make Teflon chemically inert, heat-resistant, and non-stick. Used in non-stick cookware, lab equipment, and industrial seals. Polyethylene = from ethene; PVC = from vinyl chloride; Polystyrene = from styrene.

🧠 Quick Memory Chart — CA06

◈ Carbon
  • Diamond: 4 bonds; 3D; hardest; insulator
  • Graphite: 3 bonds; layers; conducts
  • Fullerene: C₆₀; 1985; drug delivery
  • Alkane: CₙH₂ₙ₊₂ (single bonds)
  • Alkene: CₙH₂ₙ (double bond)
💧 Everyday Chem
  • Soap: fat + NaOH (saponification)
  • Micelles: non-polar tail in grease
  • Detergent works in hard water
  • Teflon: tetrafluoroethene (addition)
  • Nylon: condensation polymer
🌿 Fertilisers
  • Urea CO(NH₂)₂: 46% N (highest)
  • Superphosphate: P fertiliser
  • KCl (muriate): K fertiliser
  • NPK = 3 major plant nutrients
  • Glass: SiO₂+Na₂CO₃+CaCO₃

📝 Practice Exercise

E1. The general formula CₙH₂ₙ₊₂ represents:
(a) Alkenes(b) Alkynes(c) Alkanes(d) Aromatic compounds
E2. PVC (polyvinyl chloride) is made from which monomer?
(a) Ethene(b) Vinyl chloride(c) Tetrafluoroethene(d) Styrene
E3. Borosilicate glass (Pyrex) is heat-resistant because it contains:
(a) Lead oxide(b) Boron trioxide (B₂O₃)(c) Potassium carbonate(d) Calcium oxide
Answers:
E1 → (c) Alkanes [saturated hydrocarbons; single bonds; CH₄, C₂H₆, C₃H₈...]  |  E2 → (b) Vinyl chloride [CH₂=CHCl; addition polymerisation to form PVC]  |  E3 → (b) Boron trioxide [B₂O₃ reduces thermal expansion; hence used for lab glassware and cookware]
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