Chemistry
🔒 Log in to trackCarbon compounds, fuels, polymers, industry and pollution
🔒 Log in to trackCarbon and its compounds
- Carbon forms long chains and rings (catenation) and has valency 4 (tetravalency).
- Allotropes: diamond (hardest, bad conductor, each C bonded to 4), graphite (soft, layered, conducts electricity — pencil 'lead', lubricant, electrodes), fullerene (C₆₀ buckminsterfullerene), graphene (single layer of graphite).
- Hydrocarbons: alkanes single bonds (CₙH₂ₙ₊₂, saturated), alkenes double bond (CₙH₂ₙ), alkynes triple bond (CₙH₂ₙ₋₂).
- Methanol is poisonous (can cause blindness); ethanol is the alcohol in drinks and is blended with petrol. Vinegar is about 5–8% acetic acid. Esters have a fruity smell.
- Soap = sodium or potassium salt of long-chain fatty acids, made by saponification (fat + NaOH). Soap forms scum in hard water; detergents work in hard water too.
- Hydrogenation of vegetable oil with a nickel catalyst gives vanaspati ghee.
Fuels
| Fuel | Main component |
|---|---|
| CNG | Methane |
| LPG | Butane (with propane); ethyl mercaptan is added for smell to detect leaks |
| Biogas / gobar gas | Methane (plus CO₂) |
| Oxy-acetylene flame | Acetylene (ethyne) — welding and cutting |
| Water gas | CO + H₂ |
| Producer gas | CO + N₂ |
- Hydrogen has the highest calorific value by mass. Octane number rates petrol; cetane number rates diesel.
- Coal by carbon content: anthracite > bituminous > lignite > peat.
- Ethylene (ethene) is used for artificial ripening of fruits (calcium carbide, which releases acetylene, is banned for this).
Polymers
| Polymer | Monomer / note |
|---|---|
| Polythene | Ethene |
| PVC | Vinyl chloride — pipes |
| Teflon | Tetrafluoroethylene — non-stick cookware |
| Bakelite | Phenol + formaldehyde — thermosetting, electrical switches |
| Nylon | First fully synthetic fibre |
| Natural rubber | Isoprene (polyisoprene) |
| Rayon | 'Artificial silk' from cellulose |
| Melamine | Thermosetting — crockery |
- Vulcanisation — heating rubber with sulphur (Charles Goodyear) to make it hard and elastic.
- Thermoplastics (polythene, PVC) soften on heating; thermosetting plastics (Bakelite, melamine) do not.
Industrial processes
| Process | Product | Catalyst |
|---|---|---|
| Haber | Ammonia | Iron |
| Contact | Sulphuric acid | Vanadium pentoxide (V₂O₅) |
| Ostwald | Nitric acid | Platinum |
| Solvay | Sodium carbonate | — |
| Chlor-alkali | NaOH, Cl₂, H₂ (electrolysis of brine) | — |
- Glass = silica (sand) + sodium carbonate + limestone, fused; borosilicate (Pyrex) resists heat; cobalt oxide gives blue glass.
- Portland cement (Joseph Aspdin); gypsum is added to slow its setting.
Pollution and poisons
| Substance | Effect |
|---|---|
| SO₂, NO₂ | Acid rain (damage to the Taj Mahal — 'marble cancer') |
| CFCs | Ozone layer depletion |
| CO₂, CH₄, N₂O, water vapour | Greenhouse effect |
| Carbon monoxide | Binds haemoglobin (carboxyhaemoglobin) — suffocation |
| Methyl isocyanate (MIC) | Bhopal gas tragedy, 1984 |
| Mercury | Minamata disease (Japan) |
| Cadmium | Itai-itai disease (Japan) |
| Arsenic | Black-foot disease; groundwater contamination |
| Excess fluoride | Fluorosis (teeth and bones) |
| Nitrate in water | Blue baby syndrome |
| Lead | Plumbism (lead poisoning) |
Carbon — the backbone chemical
Carbon bonds to itself in long chains and rings (catenation) and always shows valency 4 (tetravalency) — together these give it millions of compounds, the field of organic chemistry. Its allotropes: diamond (hardest natural substance, does not conduct, each C bonded to 4 others), graphite (soft, slippery, conducts electricity — pencil 'lead', electrodes, lubricant), fullerene (C₆₀) and graphene (one-atom-thick sheet). Hydrocarbons: alkanes — single bonds, saturated, CₙH₂ₙ₊₂ (methane CH₄, ethane); alkenes — one double bond, CₙH₂ₙ (ethene); alkynes — one triple bond, CₙH₂ₙ₋₂ (ethyne = acetylene).
Fuels — what burns in what
| Fuel | Main component |
|---|---|
| CNG | Methane |
| LPG | Butane (+ propane); ethyl mercaptan added for smell |
| Biogas (gobar gas) | Methane (+ CO₂) |
| Oxy-acetylene flame | Ethyne (acetylene) — welding/cutting (~3000 °C) |
| Water gas | CO + H₂ |
| Producer gas | CO + N₂ |
| Coal grades rise with carbon: peat → lignite → bituminous → anthracite (best). Petroleum ('black gold') is separated by fractional distillation into refinery gas, petrol, naphtha, kerosene, diesel, lubricating oil and bitumen (road tar, residue). |
Everyday carbon compounds
- Methanol (wood spirit) is poisonous — even small doses cause blindness; ethanol is drinkable alcohol, blended into petrol.
- Vinegar = 5–8% acetic acid. Esters (acid + alcohol) give fruits their smell.
- Soap = sodium/potassium salt of a long-chain fatty acid, made by saponification (fat + NaOH). In hard water soap forms useless scum; detergents work even in hard water.
- Hydrogenation: vegetable oil + H₂ with a nickel catalyst → vanaspati ghee (solid fat).
Industrial processes — name ↔ product
| Process | Product |
|---|---|
| Haber | Ammonia (N₂ + 3H₂, iron catalyst) |
| Contact | Sulphuric acid (V₂O₅ catalyst) |
| Ostwald | Nitric acid (from ammonia, Pt catalyst) |
| Solvay | Sodium carbonate (washing soda) |
| Bosch | Hydrogen (from water gas) |
Polymers and fibres
Polymers are giant molecules of repeating units. Natural: cotton (cellulose), silk and wool (proteins), starch, natural rubber. Vulcanisation (Charles Goodyear, 1839) heats rubber with sulphur — tyres get strength and elasticity. Synthetic: polythene (from ethene — bags), PVC (pipes, insulation), Teflon/PTFE (non-stick pans), nylon (first fully synthetic fibre, 1935 — ropes, parachutes), bakelite (first plastic, hard, thermosetting — switch boards), rayon ('artificial silk', made from wood cellulose).
Pollution — pollutant ↔ effect
- Carbon monoxide (CO) binds haemoglobin ~200 times more strongly than O₂ → suffocation deaths from geysers and coal stoves.
- SO₂ and NOₓ → acid rain; SO₂ was the killer of the London smog (1952).
- Mercury → Minamata disease; cadmium → itai-itai disease (both Japan, 1950s–60s).
- CFCs (old fridge/aerosol gases) ate the ozone layer — phased out by the Montreal Protocol (1987); the ozone layer lies in the stratosphere.
- Greenhouse gases (CO₂, CH₄, water vapour) drive global warming; the Kyoto Protocol (1997) and Paris Agreement (2015) target emissions. The Bhopal gas tragedy (1984) was methyl isocyanate (MIC).
Question types you will see
Each type: how to recognise it, the method step by step, and one question to try.
Fuel ↔ main component
'CNG is mainly…', 'LPG contains…', 'why does LPG smell', 'which gas is used in welding', 'best variety of coal'.
Gas family: CNG and biogas = methane; LPG = butane (+ propane); welding = acetylene (ethyne) with oxygen.
LPG leaks are smellable because ethyl mercaptan is added — the gas itself is odourless.
Coal ranking by carbon: peat < lignite < bituminous < anthracite; petroleum splits by fractional distillation (bitumen last).
each fuel is a named hydrocarbon, so the answer is recall plus the one-line use.
The gas used with oxygen in a welding torch is —
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Acetylene (ethyne) — its oxy-acetylene flame reaches about 3000 °C and cuts steel.
Industrial process ↔ product
'Haber process gives…', 'sulphuric acid is made by the … process', 'Ostwald process produces…', match-the-column of processes and chemicals.
Fix the four: Haber → ammonia; Contact → sulphuric acid; Ostwald → nitric acid; Solvay → sodium carbonate.
Catalyst tags: Haber–iron, Contact–V₂O₅, Ostwald–platinum.
In match-the-columns, anchor on ammonia (Haber) — the rest fall into place by elimination.
The Contact process manufactures —
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Sulphuric acid (H₂SO₄) — SO₂ is oxidised to SO₃ over a V₂O₅ catalyst, then absorbed in water.
Polymers, plastics and fibres
'First synthetic fibre / first plastic', 'Teflon is used for…', 'vulcanisation of rubber is done with…', 'rayon is called artificial…', natural vs synthetic classification.
Records: nylon = first fully synthetic fibre; bakelite = first plastic (thermosetting); rayon = artificial silk from cellulose.
Uses: polythene–bags, PVC–pipes, Teflon–non-stick, nylon–ropes and parachutes.
Vulcanisation = natural rubber + sulphur (Goodyear) → tyres.
Natural fibres: cotton–cellulose; silk/wool–protein; synthetic: nylon, polyester, acrylic.
Vulcanised rubber is made by heating natural rubber with —
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Sulphur — cross-links form between chains, making the rubber strong, elastic and heat-resistant (tyres).
Allotropes and hydrocarbon families
'Which allotrope of carbon conducts electricity', 'hardest natural substance', 'alkane/alkene/alkyne general formula', 'which hydrocarbon is saturated'.
Allotropes: diamond (hardest, non-conductor), graphite (soft, conducts), fullerene C₆₀, graphene.
Families: alkane CₙH₂ₙ₊₂ (single bonds, saturated); alkene CₙH₂ₙ (double); alkyne CₙH₂ₙ₋₂ (triple).
Methane (CH₄) is the simplest alkane and the main gas in CNG/biogas.
Which general formula belongs to an alkyne?
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CₙH₂ₙ₋₂ — the triple bond (as in acetylene, C₂H₂) leaves fewer hydrogens than an alkene.
Everyday carbon chemistry
'Which alcohol causes blindness', 'vinegar contains…', 'why does soap fail in hard water', 'hydrogenation of oils uses which catalyst', 'esters give…'.
Alcohols: methanol = poison (blindness, death); ethanol = the alcohol in drinks and petrol blends.
Vinegar = 5–8% acetic acid; esters (acid + alcohol) = fruity smells.
Soap = fatty-acid salt made by saponification; forms scum with hard-water Ca²⁺/Mg²⁺ — detergents do not.
Hydrogenation of vegetable oil uses a nickel catalyst → vanaspati.
Soap does not lather well in hard water because —
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Ca²⁺/Mg²⁺ ions react with soap to form insoluble scum; synthetic detergents are made to work even so.
Pollutant ↔ disease or event
'Minamata disease is caused by…', 'which gas causes acid rain', 'CFCs damage…', 'Bhopal gas tragedy leaked…', 'why is CO poisonous'.
Japanese diseases: Minamata–mercury; itai-itai–cadmium.
CO binds haemoglobin far more strongly than oxygen → carbon monoxide poisoning.
SO₂ + NOₓ → acid rain; CFCs → ozone-hole (Montreal Protocol 1987); Bhopal 1984 leaked methyl isocyanate (MIC).
Greenhouse gases: CO₂, CH₄ — Kyoto 1997, Paris 2015.
Minamata disease resulted from poisoning by —
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Mercury — factory effluent in Japan entered fish, and fish-eating villagers were poisoned. (Cadmium caused itai-itai.)
Formula sheet
iron catalyst
Shortcuts that save time
Pair the catalysts too: Haber — Fe, Contact — V₂O₅, Ostwald — Pt.
Which catalyst is used in the Contact process?
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Vanadium pentoxide (V₂O₅).
Minamata — Mercury; Itai-itai ('ouch-ouch', bone pain) — Cadmium.
Mistakes to avoid
Where most students lose marks on this subtopic.
Saying LPG is mainly methane — LPG is mainly butane; CNG and biogas are mainly methane.
Calling Bakelite a thermoplastic — it is thermosetting.
Naming phosgene for the Bhopal tragedy — the gas was methyl isocyanate.
Quick revision
Read this the night before the exam.
CNG/biogas–methane; LPG–butane (smelly ethyl mercaptan); welding–acetylene; anthracite–best coal.
Haber–NH₃, Contact–H₂SO₄, Ostwald–HNO₃, Solvay–Na₂CO₃.
Nylon first synthetic fibre; bakelite first plastic; vulcanisation = rubber + sulphur; Teflon non-stick.
Methanol poison, ethanol safe-ish; soap scums in hard water, detergent does not; hydrogenation uses nickel.
CO–haemoglobin poison; Minamata–Hg; itai-itai–Cd; CFC–ozone (Montreal 1987); Bhopal–MIC 1984.
Practice: 22 questions
Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.
Topic test · 10 questions
Suggested time 3 min · wrong answers go to your mistake notebook automatically.