Chapter 18
Chemical Reactions & Industrial Applications
Combustion, neutralisation, electrolysis, alloys, cement, glass.
Full Chapter Notes
Source · FPSC Trap Decoder · CSS MPT Smart Notes (2026 Edition)
18.1 Context
| Indicator | Value |
|---|---|
| MPT Weightage | 3–5 Marks |
| Difficulty Level | Medium |
| Confirmed Past Papers | 2022 · 2023 · 2024 · 2025 |
Trend Alert. Silicon = semiconductors/electronics appeared MPT 2025. Thermite reaction = welding appeared MPT 2024. Galvanization = zinc coating appeared MPT 2023. Hydrogenation = liquid oil to solid ghee appeared MPT 2023. LEO-GER (oxidation/reduction) appeared MPT 2022. Applied chemistry is tested as problem-solution — know which process solves which industrial problem.
18.2 High-Yield Fact Snapshot
| FPSC-Tested Fact | Correct Answer | Year Tested |
|---|---|---|
| Galvanization = coating iron with | Zinc (not copper, not tin) | 2023 — Repeated |
| Hydrogenation converts | Liquid vegetable oil → Solid Ghee | 2023 — Repeated |
| Oxidation (electron transfer) | Loss of Electrons (LEO) | 2022 |
| Reduction (electron transfer) | Gain of Electrons (GER) | 2022 |
| Silicon — primary use | Semiconductors / Electronics / Chips | 2025 |
| Thermite reaction — primary use | High-temperature welding of railway tracks | 2024 |
| Silica — primary role | Main raw material in glass manufacturing | 2024 |
| Catalyst for hydrogenation | Nickel (Ni) | High-yield |
| Zinc as sacrificial metal | More reactive than iron — corrodes first, protects iron | Galvanization logic |
| Nitrogen in chip packets | Prevents oxidation/rancidity — keeps food fresh | Application logic |
18.3 Key Chemical Processes — The Reaction Logic Matrix
| Process | Definition | MPT Application | FPSC Strategic Note |
|---|---|---|---|
| Oxidation | Loss of Electrons (LEO) | Rusting of iron; food spoilage; combustion | MPT 2022. Remember: LEO the lion says GER |
| Reduction | Gain of Electrons (GER) | Metal extraction; charging batteries | Opposite of oxidation. Always occurs with oxidation (Redox) |
| Hydrogenation | Adding Hydrogen (H₂) to unsaturated compound | Liquid oil → Solid Ghee. Catalyst = Nickel | MPT 2023. Increases SATURATION = raises melting point |
| Galvanization | Coating iron with Zinc to prevent rusting | Iron pipes, zinc-coated sheets, galvanised wire | MPT 2023. Zinc = sacrificial anode — more reactive than Fe |
| Dehydration | Removal of water from a compound | Food preservation; industrial drying | Prevents microbial growth by removing moisture |
| Thermite Reaction | Al + metal oxide → extreme heat + liquid metal | Railway track welding; heavy machinery repair | MPT 2024. Aluminum reduces iron oxide. Temperature ~3000°C |
The most reliable memory hook for redox chemistry: LEO the lion says GER. Loss of Electrons = Oxidation. Gain of Electrons = Reduction. In any redox reaction, both occur simultaneously — one species loses electrons (gets oxidised) while another gains them (gets reduced).
18.4 Galvanization — The Sacrificial Protection
Galvanization is the process of coating iron with zinc to prevent rusting. This appeared in MPT 2023. Know why zinc works — it is more reactive than iron.
| Aspect | Key Fact | FPSC Strategic Significance |
|---|---|---|
| Coating Metal | Zinc (Zn) — not copper, not tin, not lead | MPT 2023. Any other metal listed = wrong |
| Why Zinc Works | Zinc is MORE REACTIVE than iron — corrodes preferentially, protecting iron | If scratched, zinc still protects (sacrificial). Copper would ACCELERATE rusting |
| Mechanism | Zinc acts as sacrificial anode — reacts with environment first | Electrochemical protection: zinc gives up electrons instead of iron |
| Applications | Galvanised iron sheets, water pipes, corrugated roofing, wire | Widely used in Pakistani construction industry |
Galvanization Coating Trap. Students often pick Copper or Tin as the galvanising metal. The correct answer is always Zinc. Copper would actually ACCELERATE iron rusting (copper is less reactive than iron in the electrochemical series). Zinc is chosen specifically because it is MORE reactive than iron and will corrode preferentially — protecting the iron beneath.
18.5 Hydrogenation — Oil to Ghee
The chemical process of adding hydrogen (H₂) to unsaturated bonds (C=C double bonds) in vegetable oils. Uses nickel as a catalyst. Converts LIQUID oils into SOLID fats (Ghee). The process increases SATURATION — which raises the melting point, making the oil solid at room temperature.
Flow: Vegetable Oil (liquid, unsaturated C=C bonds) → add H₂ gas + Nickel catalyst + heat → Hydrogenation (double bonds become single bonds) → Saturation increases → Solid Ghee (saturated fat, higher melting point).
18.6 Industrial Materials
| Material | Key Property | FPSC Application |
|---|---|---|
| Silicon (Si) | Semiconductor — conducts electricity under certain conditions | MPT 2025. Foundation of electronics, microchips, solar cells. King of Chips |
| Silica (SiO₂) | Main component of glass and quartz | MPT 2024. Main raw material for glass. Found in sand |
| Silicon vs Silicone | Silicon = element (chips). Silicone = polymer (sealants, rubber) | Common FPSC trap — these are completely different materials |
| Thermite Mixture | Aluminum powder + Iron Oxide (Fe₂O₃) | MPT 2024. Al reduces Fe₂O₃ → releases extreme heat (~3000°C) + liquid iron |
| Nickel (Ni) | Catalyst for hydrogenation | Used in vegetable oil to ghee conversion. Also in batteries |
Silicon vs Silicone Trap. Silicon (Si) = chemical ELEMENT — foundational semiconductor used in computer chips, solar panels, and electronics. FPSC 2025: 'Which is the primary semiconductor?' → Silicon. Silicone = synthetic POLYMER (polydimethylsiloxane) — used in sealants, medical implants, cooking utensils, and rubber products. Completely different materials with entirely different uses.
18.7 Battle Card — 5-Minute Revision
| Fact | Answer |
|---|---|
| LEO-GER rule | Loss of Electrons = Oxidation | Gain of Electrons = Reduction (MPT 2022) |
| Galvanization = coating iron with | Zinc (Zn) — sacrificial anode (MPT 2023) |
| Why zinc in galvanization | More reactive than iron — corrodes first, protects iron |
| Hydrogenation converts | Liquid oil → Solid Ghee. Catalyst = Nickel (MPT 2023) |
| Hydrogenation increases | Saturation — raises melting point |
| Silicon primary use | Semiconductors / microchips / solar cells (MPT 2025) |
| Silica (SiO₂) primary use | Main raw material in glass manufacturing (MPT 2024) |
| Silicon vs Silicone | Silicon = element (chips). Silicone = polymer (sealants) |
| Thermite reaction | Aluminum + Iron Oxide → extreme heat + liquid iron (MPT 2024) |
| Thermite reaction used for | High-temperature welding of railway tracks |
| Nitrogen in chip packets | Inert gas — prevents oxidation/rancidity |
| Oxidation causes | Rusting of iron; food going stale; combustion |
| Dehydration removes | Water from compounds — food preservation |
18.8 Practice MCQs — FPSC Level
Part A — Basic Recall
Direct recall of confirmed FPSC facts (Q1–Q4).
The process of coating iron with Zinc to prevent rusting is called:
Show explanation
Galvanization is the process of coating iron with zinc to prevent rusting. Zinc forms a physical barrier AND acts as a sacrificial anode. Vulcanization = rubber treatment. Hydrogenation = oil to ghee. Oxidation = the process causing rust.
MPT 2023
In redox reactions, oxidation is defined as the:
Show explanation
Oxidation = Loss of Electrons (LEO rule). In the iron rusting reaction, iron loses electrons and is oxidised. The LEO-GER mnemonic: LEO the lion says GER — Loss of Electrons = Oxidation; Gain of Electrons = Reduction.
MPT 2022 — LEO rule
Vegetable oil is converted into vegetable ghee by the process of:
Show explanation
Hydrogenation adds hydrogen (H₂) to the C=C double bonds in unsaturated vegetable oils, converting them from liquid to solid (ghee/margarine). The catalyst is nickel (Ni). The process increases molecular saturation, raising the melting point.
MPT 2023
Silicon is the foundational material for which major industry?
Show explanation
Silicon is a semiconductor — it can conduct electricity under certain conditions. Its unique electronic properties make it the foundational material for computer chips, transistors, solar cells, and all electronic devices. Known as the 'King of Chips'.
MPT 2025
Part B — Trap-Based
Application traps with attractive distractors (Q5–Q8).
Zinc protects iron pipes by acting as a:
Show explanation
Zinc acts as a sacrificial anode in galvanization — it is more reactive than iron and will undergo corrosion (oxidation) preferentially, protecting the iron beneath. Even if the zinc coating is scratched, zinc continues to protect the exposed iron electrochemically.
Trap: Zinc = sacrificial anode — corrodes instead of iron
The primary raw material used in glass manufacturing is:
Show explanation
Silica (SiO₂ — silicon dioxide) is the main raw material for glass manufacturing. It is abundant in sand and quartz. During glass making, silica is melted with other additives (sodium carbonate, calcium carbonate) to produce the final glass product.
MPT 2024
The thermite reaction is primarily used in:
Show explanation
The thermite reaction (aluminum + iron oxide → aluminum oxide + liquid iron + enormous heat) is used for high-temperature welding — particularly repairing railway tracks in situ. The reaction reaches ~3000°C, producing liquid iron that fills gaps in the metal.
MPT 2024
In terms of electron transfer, reduction involves the:
Show explanation
Reduction = Gain of Electrons (GER rule). In electrochemical terms, a species that gains electrons is reduced. In practical terms, reduction removes oxygen from metal oxides during extraction (e.g., Fe₂O₃ + CO → Fe + CO₂, where iron is reduced).
Trap: GER rule — Gain of Electrons = Reduction
Part C — Elite Simulation
Multi-statement and galvanic coupling questions (Q9–Q12).
Consider galvanization: (1) It provides a physical zinc barrier over iron. (2) Zinc is more reactive than iron. (3) Zinc prevents rusting by acting as a sacrificial metal. Which are correct?
Show explanation
Zinc protects iron both as a physical barrier (when coating is intact) and as a sacrificial anode (when scratched). Statement 1 alone is incomplete — both mechanisms together form the complete protection system.
Trap: All three correct — complete galvanization logic
Consider: (1) Oxidation = Loss of Electrons. (2) Reduction = Gain of Electrons. (3) Dehydration = Removal of Water. Which are correct?
Show explanation
All three definitions are correct standard chemical definitions: Oxidation = loss of electrons (LEO). Reduction = gain of electrons (GER). Dehydration = removal of water. This appeared in MPT 2025.
MPT 2025 — all three correct
A chemical process adds hydrogen to liquid oil using nickel as catalyst, producing solid fat. This process results in:
Show explanation
Hydrogenation adds H₂ to C=C double bonds in unsaturated oils, converting them to single bonds (saturation increases). More saturated fats have higher melting points — explaining why liquid oil becomes solid ghee. The process does NOT increase unsaturation or decrease melting point.
Trap: Hydrogenation = increased saturation = raised melting point
If iron is connected to copper in moist conditions (galvanic coupling), which metal will corrode faster?
Show explanation
In a galvanic couple between iron and copper, iron is the less noble metal (higher in the electrochemical activity series than copper). The less noble metal acts as the anode and corrodes preferentially.
Trap: Iron is less noble than copper — corrodes faster in galvanic couple
Answer Key with Trap Analysis
Chemical Reactions & Industrial Applications (Q1–Q12)
| Q | Correct | Type | Primary Trap | Why Others Fail |
|---|