Industrial & Electrochemistry
Industrial chemistry applies chemical reactions at large scale to manufacture essential products. Electrochemistry links chemistry with electricity — both producing and using electrical energy.
A. Key Industrial Processes
Haber Process — Ammonia
N₂ + 3H₂ ⇌ 2NH₃
⚙️ 450°C · 200 atm · Iron (Fe) catalyst
Produces ammonia (NH₃) — used to make fertilisers (urea, ammonium nitrate), explosives, and cleaning products. One of the most important industrial processes globally.
Contact Process — Sulfuric Acid
2SO₂ + O₂ ⇌ 2SO₃ → H₂SO₄
⚙️ 450°C · Vanadium pentoxide (V₂O₅) catalyst · SO₃ absorbed in H₂SO₄ then diluted
Produces H₂SO₄ — the most widely produced industrial chemical. Used in fertilisers, car batteries, paints, dyes, and detergents.
Solvay Process — Sodium Carbonate
NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ → Na₂CO₃
⚙️ Moderate conditions · CO₂ from limestone (CaCO₃ heating)
Produces Na₂CO₃ (washing soda / soda ash) — used in glass making, detergents, paper, and water softening.
Chlor-Alkali Process
2NaCl(aq) + 2H₂O → Cl₂ + H₂ + 2NaOH
⚙️ Electrolysis of brine (NaCl solution)
Produces Cl₂ (disinfectants, PVC, bleach), H₂ (fuel, ammonia), and NaOH (soap, paper, aluminium production).
Cracking of Hydrocarbons
Long-chain alkanes → shorter alkenes + alkanes
⚙️ High temperature OR catalytic cracking (zeolite catalyst, lower temp)
Breaks long-chain molecules from crude oil into useful shorter ones — produces petrol (gasoline) and ethene (for plastics, ethanol).
⚡ MCQ Tip Haber = NH₃ (iron catalyst, 450°C, 200 atm). Contact = H₂SO₄ (V₂O₅ catalyst, 450°C). Solvay = Na₂CO₃. Chlor-alkali = Cl₂ + H₂ + NaOH from brine electrolysis. Cracking = long → short chains.
B. Petroleum & Fractional Distillation
Crude Oil Fractions — Boiling Point Order
Separated by fractional distillation — lower fractions rise higher in the column (lower BP)
| Fraction | Boiling Point | Carbon Chain | Main Use |
|---|---|---|---|
| Refinery Gas | < 25°C | C₁–C₄ | Fuel (LPG — cooking, heating) |
| Gasoline (Petrol) | 25–75°C | C₅–C₉ | Car fuel |
| Naphtha | 75–190°C | C₆–C₁₀ | Chemical feedstock, dry cleaning |
| Kerosene (Paraffin) | 190–250°C | C₁₀–C₁₆ | Jet fuel, heating oil |
| Diesel | 250–350°C | C₁₄–C₂₀ | Diesel engines, trucks |
| Fuel Oil / Lubricating Oil | > 350°C | C₂₀+ | Ship fuel, engine lubricants |
| Bitumen (Residue) | Non-volatile | C₇₀+ | Road surfacing, waterproofing |
Refinery Gas
Boiling Point< 25°C
Carbon ChainC₁–C₄
Main UseFuel (LPG — cooking, heating)
Gasoline (Petrol)
Boiling Point25–75°C
Carbon ChainC₅–C₉
Main UseCar fuel
Naphtha
Boiling Point75–190°C
Carbon ChainC₆–C₁₀
Main UseChemical feedstock, dry cleaning
Kerosene (Paraffin)
Boiling Point190–250°C
Carbon ChainC₁₀–C₁₆
Main UseJet fuel, heating oil
Diesel
Boiling Point250–350°C
Carbon ChainC₁₄–C₂₀
Main UseDiesel engines, trucks
Fuel Oil / Lubricating Oil
Boiling Point> 350°C
Carbon ChainC₂₀+
Main UseShip fuel, engine lubricants
Bitumen (Residue)
Boiling PointNon-volatile
Carbon ChainC₇₀+
Main UseRoad surfacing, waterproofing
⚡ MCQ Tip Longer carbon chain = higher boiling point = collected lower in the column. Shorter chain = more flammable, lower viscosity, lower BP. Fractional distillation separates by BOILING POINT difference.
C. Electrochemistry
Electrolysis vs Galvanic Cells
⚡ Electrolytic Cell
- Uses electrical energy to drive a NON-spontaneous reaction
- External power source (battery) required
- Used in: electroplating, extraction of metals, production of Cl₂
🔋 Galvanic (Electrochemical) Cell
- Converts chemical energy into electrical energy (spontaneous)
- No external power needed — reaction generates EMF
- Example: Daniell cell (Zn anode, Cu cathode)
| Electrode | Charge | Process | Ions attracted |
|---|---|---|---|
| Cathode | Negative (−) | Reduction — gains electrons | Cations (positive ions) |
| Anode | Positive (+) | Oxidation — loses electrons | Anions (negative ions) |
Mnemonic
AN OX — RED CAT
ANOde = OXidation · CATHode = REDuction
D. Faraday's Laws & Applications of Electrolysis
Faraday's Laws of Electrolysis
| Law | Statement |
|---|---|
| First Law | The mass of substance deposited at an electrode is directly proportional to the quantity of electric charge passed (Q = It) |
| Second Law | For the same quantity of charge, the masses deposited are proportional to their equivalent weights (molar mass ÷ valency) |
| Application | Electrolyte | Products / Purpose |
|---|---|---|
| Electroplating | Solution of the plating metal salt | Thin metal coating deposited on object (e.g. chrome on steel, gold on jewellery) |
| Extraction of Aluminium | Molten Al₂O₃ (bauxite) in cryolite | Pure aluminium metal at cathode — only economical method |
| Production of Chlorine | Brine (NaCl solution) | Cl₂ at anode, H₂ at cathode, NaOH in solution |
| Refining of Copper | CuSO₄ solution | Pure copper deposited at cathode; impure copper dissolves at anode |
⚡ MCQ Tip AN OX — RED CAT (Anode=Oxidation, Cathode=Reduction). Galvanic cell = chemical → electrical. Electrolytic cell = electrical → chemical. Aluminium extraction uses molten bauxite (NOT aqueous — water would be electrolysed instead).
Quick MCQ Revision
| Fact | Answer |
|---|---|
| Haber process | N₂ + 3H₂ ⇌ 2NH₃ — iron catalyst, 450°C, 200 atm |
| Contact process | 2SO₂ + O₂ ⇌ 2SO₃ → H₂SO₄ — V₂O₅ catalyst, 450°C |
| Chlor-alkali products | Cl₂ (anode) + H₂ (cathode) + NaOH (solution) |
| AN OX — RED CAT | Anode = Oxidation · Cathode = Reduction |
| Galvanic cell converts | Chemical energy → Electrical energy (spontaneous) |
| Electrolytic cell uses | Electrical energy → Chemical energy (non-spontaneous) |
| Longest carbon chain fraction | Bitumen (C₇₀+) — road surfacing, non-volatile |
| Jet fuel fraction | Kerosene (C₁₀–C₁₆, BP 190–250°C) |
| Cracking produces | Short-chain alkenes + alkanes from long-chain alkanes |