NDA Chemistry · Free notes
Carbon and Its Compounds — NDA Chemistry
Carbon is the largest chapter in NDA Chemistry — 46 PYQs across 2017–2026, almost all EASY or MODERATE, and almost all pure named-fact recall. Two questions in three are 'which statement is NOT correct' about an allotrope or a common compound, so the win comes from knowing the table cold, not from a derivation. The chapter teaches in six movements, building from why carbon is special up to its everyday products: (1) Tetra-valency, catenation and isomerism — the two properties (four bonds + self-linking) that explain why carbon forms more compounds than every other element combined; (2) Allotropes — diamond, graphite, fullerene and graphene, their structures, and the property statements the bank loves to falsify; (3) Hydrocarbons and organic classification — the homologous series, their general formulas, and the organic-vs-inorganic line Wöhler erased; (4) Functional groups and common organic compounds — the group↔family↔property table plus carbon monoxide; (5) Common carbon compounds and pigments — name↔formula↔use, water of crystallization, and pigments; (6) Soaps, detergents and hydrogenation of oils — saponification, micelles, why detergents beat soap in hard water, and how oils become margarine. 15 concepts, every PYQ tagged. Most concepts are reference tables: memorise the table, win the marks.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Tetra-valency, Catenation and Isomerism
4 PYQsCarbon forms four covalent bonds and links to itself in chains and rings, so a handful of atoms can be arranged many different ways — which is why carbon has more compounds than any other element.
Allotropes of Carbon
15 PYQsThe same element, carbon, crystallises in different structures — diamond, graphite, fullerene and graphene — each with its own bonding and dramatically different properties.
Hydrocarbons and Organic Classification
3 PYQsHydrocarbons are compounds of only carbon and hydrogen, grouped into homologous series (alkanes, alkenes, alkynes) each with its own general formula and trends.
Functional Groups and Common Organic Compounds
9 PYQsA functional group is the reactive part of an organic molecule that decides its family and properties — alcohols, acids, esters — plus a handful of named compounds the bank tests on sight.
Common Carbon Compounds and Pigments
10 PYQsThe everyday names, formulas and uses of carbonate and bicarbonate compounds, their waters of crystallization, and the pigments used in paints.
Soaps, Detergents and Hydrogenation of Oils
5 PYQsSoap is the sodium or potassium salt of a long-chain fatty acid; detergents do the same job with a synthetic head that survives hard water; hydrogenation turns liquid oils into solid fats.
Formula & revision sheet
2 formulas · 12 reference tables · 13 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
2 formulas · 12 reference tables · 13 gotchas across all subtopics — the exam-eve cheat-sheet
Watch out for (3)
- Carbon forms a triple bond, not a 'four' bond→ Why carbon forms so many compounds
- Covalent means poor conductor→ Why carbon forms so many compounds
- Pentane has 3 isomers, not 5→ Structural isomerism and counting isomers
Reference tables (2)
Crystalline allotropes — structure, hybridisation and properties4 rows
| Allotrope | Structure / hybridisation | Key property | Use / identity |
|---|---|---|---|
| Diamond | 3-D tetrahedral network, sp³ | Hardest natural substance; electrical insulator | Cutting/abrasives; isomorphous with silicon Diamond does NOT conduct electricity — all four electrons are locked in covalent bonds. |
| Graphite | Flat hexagonal sheets, sp² | Soft, slippery; good conductor; most stable form | Pencil lead, lubricant, electrodes |
| Fullerene (C₆₀) | Closed cage (football), sp² | Purest form of carbon | Nanotechnology, lubricants |
| Graphene | Single one-atom-thick sheet, sp² | Thinnest and strongest material | Electronics, composites |
Property traps and impure forms of carbon5 rows
| Common false claim | The truth |
|---|---|
| Diamond conducts electricity | Insulator — no free electrons |
| Graphite is the second-hardest substance | Soft and slippery (a lubricant) |
| Graphite layers held by covalent single bonds | Held by weak van der Waals forces |
| Diamond and graphite differ chemically | Same element → same chemistry; only physical properties differ Allotropes are the SAME element, so they always share chemical properties — only physical properties change. |
| Fly ash is an allotrope of carbon | A combustion residue, not an allotrope |
Watch out for (3)
- Graphite is sp², diamond is sp³→ Crystalline allotropes — structure, hybridisation and properties
- Only fullerene is cage-like→ Crystalline allotropes — structure, hybridisation and properties
- Allotropes share chemistry, not physics→ Property traps and impure forms of carbon
Reference tables (1)
Organic vs inorganic — and Wöhler's synthesis4 rows
| Compound | Organic or inorganic | Note |
|---|---|---|
| Marsh gas (methane, CH₄) | Organic | Simplest alkane |
| Urea | Organic | First lab-synthesised organic compound (Wöhler, 1828) Wöhler made urea FROM ammonium cyanate — the product is organic, the starting salt is inorganic. |
| Cane sugar (sucrose) | Organic | A carbohydrate |
| Ammonium cyanate (NH₄OCN) | Inorganic | An ionic salt — Wöhler's precursor |
Watch out for (2)
- CₙH₂ₙ is shared by alkenes and cycloalkanes→ Homologous series and general formulas
- The starting salt is inorganic, the product is organic→ Organic vs inorganic — and Wöhler's synthesis
Reference tables (3)
Functional groups and their families4 rows
| Family | Functional group | Example | Giveaway property |
|---|---|---|---|
| Alcohol | -OH | Ethanol | Neutral to litmus Ethanol does NOT turn litmus red — alcohols are neutral, unlike acids. |
| Carboxylic acid | -COOH | Acetic acid; formic (methanoic) acid | Sour; turns blue litmus red |
| Ester | -COO- | Ethyl acetate | Sweet, fruity smell |
| Aldehyde / Ketone | -CHO / C=O | Formaldehyde / Acetone | Reactive carbonyl group |
Carbon monoxide and other named facts3 rows
| Fact | Detail |
|---|---|
| CO is poisonous because… | It binds haemoglobin (carboxyhaemoglobin), blocking O₂ transport CO is dangerous because of its affinity for haemoglobin — not because it is acidic. CO is a neutral oxide. |
| Litmus is derived from… | Lichens |
| Element forming the most compounds | Carbon |
Common compounds — formula and use2 rows
| Common name | Formula | Key fact / use |
|---|---|---|
| Baking soda | NaHCO₃ | Decomposes on heating → CO₂ makes cakes rise It is the released CO₂ — not water vapour — that raises the dough. |
| Gypsum | CaSO₄·2H₂O | Two waters of crystallization; used to make plaster of Paris |
Watch out for (1)
- Alcohol is neutral, acid turns litmus red→ Functional groups and their families
Reference tables (3)
Common names, formulas and uses6 rows
| Common name | Chemical name / formula | Use or identity |
|---|---|---|
| Washing soda | Na₂CO₃·10H₂O | Cleaning, water softening |
| Baking soda | NaHCO₃ | Baking, antacid |
| Dry ice | Solid CO₂ | Refrigerant — sublimes, no liquid Dry ice is solid carbon dioxide, NOT frozen water. |
| Chalk / Marble | CaCO₃ | Building, blackboard chalk |
| Vinegar | Acetic (ethanoic) acid | Food preservative, flavouring |
| Silica gel | SiO₂ (hydrated) | Desiccant — absorbs moisture |
Water of crystallization4 rows
| Salt | Formula | Water molecules |
|---|---|---|
| Blue vitriol (copper sulphate) | CuSO₄·5H₂O | 5 |
| Washing soda | Na₂CO₃·10H₂O | 10 |
| Gypsum | CaSO₄·2H₂O | 2 |
| Plaster of Paris | (CaSO₄)₂·H₂O | 1 (shared by two CaSO₄ units) Plaster of Paris has ONE water of crystallization per TWO formula units of CaSO₄ — i.e. CaSO₄·½H₂O. |
Pigments and carbon black5 rows
| Substance | Pigment? | Note |
|---|---|---|
| Zinc oxide | Yes (white) | Common white pigment |
| White lead | Yes (white) | Traditional white pigment |
| Chalk (CaCO₃) | Yes (white) | Cheap white pigment/filler |
| Silica | No | A filler/abrasive, not a pigment Of zinc oxide, chalk, white lead and silica, the odd one out (NOT a pigment) is silica. |
| Carbon black | Yes (black) | Made by incomplete combustion of hydrocarbons |
Watch out for (2)
- Dry ice is CO₂, not ice→ Common names, formulas and uses
- Plaster of Paris = half a water per CaSO₄→ Water of crystallization
Reference tables (3)
Soaps, saponification and micelles4 rows
| Feature | Detail |
|---|---|
| What a soap is | Na or K salt of a long-chain fatty acid |
| Two ends of the molecule | Hydrophobic tail + hydrophilic (ionic) head |
| Micelle orientation | Tails inward onto oil; ionic heads outward into water The ionic heads face the WATER, not the oil — the common trap reverses this. |
| NaOH vs KOH in saponification | NaOH → hard soap; KOH → soft (liquid) soap |
Detergents vs soaps3 rows
| Soap | Synthetic detergent | |
|---|---|---|
| Head group | Carboxylate (-COO⁻Na⁺) | Sulphonate or quaternary ammonium |
| Source | Natural fats/oils | Petrochemicals (synthetic) |
| Works in hard water? | No — forms scum | Yes Sodium stearate is a SOAP, not a detergent — the carboxylate head gives it away. |
Hydrogenation of oils1 rows
| Starting material | Reagent / catalyst | Product |
|---|---|---|
| Unsaturated vegetable oil (liquid) | H₂ gas, nickel catalyst | Saturated fat (solid) — margarine / vanaspati The reagent is HYDROGEN gas (with a Ni catalyst) — that is what 'hydrogenation' means. |
Watch out for (2)
- Micelle: ionic heads face the water→ Soaps, saponification and micelles
- The carboxylate is the soap→ Detergents vs soaps
PYQ weightage by concept
15 concepts · 46 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
15 concepts · 46 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Why carbon forms so many compounds | 3 | 7% |
| Structural isomerism and counting isomers | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| Crystalline allotropes — structure, hybridisation and properties | 9 | 20% |
| Property traps and impure forms of carbon | 6 | 13% |
| Concept | PYQs | Share |
|---|---|---|
| Homologous series and general formulas | 2 | 4% |
| Organic vs inorganic — and Wöhler's synthesis | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| Functional groups and their families | 4 | 9% |
| Carbon monoxide and other named facts | 3 | 7% |
| Common compounds — formula and use | 2 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Common names, formulas and uses | 6 | 13% |
| Water of crystallization | 2 | 4% |
| Pigments and carbon black | 2 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Soaps, saponification and micelles | 3 | 7% |
| Detergents vs soaps | 1 | 2% |
| Hydrogenation of oils | 1 | 2% |
Test yourself on Carbon and Its Compounds
15 past NDA questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.