Curriculum
Chemistry
Chapter 1 - Transition Elements and Iron Metallurgy
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1.1Where they are in the periodic table1.2The main transition elements (d-block)1.3The four transition series1.4Economic importance of the first-series elements1.5Electron configurations of the first series1.6Rules for filling1.7Configurations of the common ions1.8Why Fe(II) is easily oxidized to Fe(III) but Mn(II) is not1.9Oxidation-state rules for the series1.10Calculating oxidation states in compounds1.11Definition of a transition element
Chapter 2 - Chemical Analysis
0/221.1Revision of concepts and laws needed in this chapter1.2Importance1.3Kinds of analysis1.4Qualitative analysis1.5A. Identification of acid radicals (anions)1.6(1) Dilute hydrochloric acid group1.7(2) Concentrated sulphuric acid group1.8(3) Barium chloride group1.9Practical differentiation between pairs of salts (typical exam type)1.10Reasoning questions1.11Detailed Comparison Matrix: Diagnostic Silver Nitrate (AgNO3) Confirmatory Matrix
Chapter 3 - Chemical Equilibrium
0/221.1The equilibrium system1.2Types of chemical reactions1.3Chemical equilibrium1.4Rate of reaction1.5Factors affecting the rate of a reaction1.6Nature of the reactants1.7Concentration and the law of mass action1.8Temperature — collision theory1.9Pressure1.10Le Chatelier's principle1.11Catalysts1.12Light
2.1Strong and weak electrolytes2.2Hydronium ion2.3Definitions2.4Ostwald's dilution law2.5Hydronium ion concentration of a weak acid2.6Hydroxide ion concentration of a weak base2.7Ionization of water and the ionic product Kw2.8pH and pOH2.9Solubility and solubility product2.10Summary of key relations
Chapter 4 - Electrochemistry
0/331.1The starting experiment: zinc in copper sulphate1.2The idea behind the galvanic cell1.3Construction of the Daniell cell1.4What happens at each electrode1.5When does the current stop?1.6The salt bridge — what it is and why it is needed1.7Why we need a reference1.8The standard hydrogen electrode1.9Standard electrode potentials1.10Measuring an electrode potential (idea of the experiment)1.11Definition1.12What the series tells us (the conclusions to know)1.13Calculating the cell emf1.14Cell notation (cell diagram)
3.1The electrolytic cell3.2Example: electrolysis of copper(II) chloride solution3.3First law3.4Second law3.5The faraday3.6The working formula3.7Worked examples3.8Electroplating3.9Extraction of aluminium3.10Electrorefining of copper3.11Galvanic cells versus electrolytic cells3.12Scientists and the value of electrochemistry
Chapter 5 - Organic Chemistry
0/721.1Historical background1.2Modern definition1.3Why are there so many organic compounds?1.4Comparison: organic and inorganic compounds1.5Molecular formula1.6Structural formula1.7Isomerism1.8Detecting carbon and hydrogen in an organic compound1.9Classification of hydrocarbons1.10Structure and the homologous series1.11Alkyl radicals (R–)1.12IUPAC nomenclature of alkanes1.13Methane — occurrence and preparation1.14Physical properties1.15Chemical properties of alkanes
5.1Functional groups5.2Alcohols and phenols — the difference5.3Nomenclature of alcohols5.4Classification of alcohols5.5Ethanol — preparation5.6Denatured (methylated) alcohol — "red spirit"5.7Physical properties5.8Chemical properties of ethanol5.9Uses of alcohols5.10Phenols5.11Preparation5.12Physical properties5.13Chemical properties5.14Tests for phenol
6.1The carboxyl group6.2Types6.3Nomenclature6.4Preparation of acetic acid6.5Physical properties6.6Chemical properties6.7Aromatic acids: benzoic acid6.8Important acids and their uses6.9Definition and formation6.10Nomenclature6.11Preparation6.12Physical properties6.13Chemical properties6.14Applications of esters6.15Aspirin6.16Types of organic reactions (summary)6.17Revision key points for Part B
7.1The birth of organic chemistry and the vital-force theory7.2Why organic compounds are so abundant7.3Organic versus inorganic compounds7.4Molecular formula, structural formula and isomers7.5Detecting carbon and hydrogen in an organic compound7.6Hydrocarbons and the alkane series7.7The alkyl radical and IUPAC naming7.8Methane, physical and chemical properties of alkanes7.9Practice with answers7.10Ministry exam traps
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Text lesson
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons
Overview
Overview
🌳 Concept tree
- Alkynes (Acetylene) and Cyclic Hydrocarbons
- ├── Structure and nomenclature
- ├── Preparation of ethyne
- ├── Properties of ethyne
- └── Cycloalkanes, CₙH₂ₙ
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 1 / 6
Structure and nomenclature
Structure and nomenclature
- Alkynes are unsaturated open-chain hydrocarbons with at least one triple bond C≡C: one strong σ bond and two weak π bonds, so alkynes are very reactive.
- General formula CₙH₂ₙ₋₂ two H fewer than the alkene and four fewer than the alkane with the same number of carbons.
- The first member is ethyne, C₂H₂, with the common name acetylene.
- Nomenclature longest chain containing the triple bond; -ane → -yne; number from the end nearer the triple bond; give the number of the first carbon of the triple bond. Examples: 3-bromo-1-butyne is CH≡C–CHBr–CH₃; 5-chloro-2-pentyne is CH₃–C≡C–CH₂–CH₂Cl; CH≡C–CH₂CH₃ 1-butyne.
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 2 / 6
Preparation of ethyne
Preparation of ethyne
Laboratory→drop water on calcium carbide (CaC₂):
CaC₂ + 2H₂O → HC≡CH + Ca(OH)₂
- Commercial calcium carbide contains impurities (calcium phosphide and sulphide), so the gas contains phosphine (PH₃) and hydrogen sulphide (H₂S); it is passed through copper sulphate solution acidified with dilute sulphuric acid (or bubbled through acidified CuSO₄) before collecting, to remove them.
- The gas is collected over water.
- Industrial from methane of natural gas heated to above 1400 °C and then cooled very rapidly (quenching):
CH₄ —(>1400 °C, rapid cooling)→ HC≡CH + 3H₂
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 3 / 6
Properties of ethyne
Properties of ethyne
| Comparison aspect | Main idea | Example | Keywords |
|---|---|---|---|
| 1. Combustion. |
| 2C₂H₂ + O₂ → 4C + 2H₂O (carbon is released as soot). In excess oxygen: 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O + heat. The oxy-acetylene flame reaches about 3000 °C and is used to weld and cut metals | limitedburnssmokyluminous |
| 2. Addition reactions | in two stages (triple → double → single bond) | — | stagestripledoublesingle |
| Comparison aspect | Main idea | Keywords |
|---|---|---|
| Hydrogenation (Ni, heat) | HC≡CH + H₂ → CH₂=CH₂ → (+H₂) CH₃–CH₃ | |
| Halogenation |
| CHBrdibromoethenethenCHBr₂ |
| Hydrogen halides |
| CHBrbromoetheneMarkovnikovCHBr₂ |
| Catalytic hydration |
| diluteH₂SO₄HgSO₄catalyst |
3. Polymerisation to benzene→3C₂H₂ → C₆H₆ when passed through a red-hot tube (~500 °C).
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 4 / 6
Cycloalkanes, CₙH₂ₙ
Cycloalkanes, CₙH₂ₙ
- Hydrocarbons with three or more carbons can form rings.
- Saturated rings are cycloalkanes, general formula CₙH₂ₙ — the same as alkenes, so cycloalkanes are isomeric with alkenes of the same carbon number (C₃H₆ is propene or cyclopropane), and one must look at the structure.
- Names put "cyclo" before the alkane name: cyclopropane C₃H₆, cyclobutane C₄H₈, cyclopentane C₅H₁₀, cyclohexane C₆H₁₂.
- Stability and ring strain. Normal tetrahedral carbon has bond angles of 109.5°. The C–C–C angle in the cyclopropane ring is 60° and in cyclobutane about 90°; this forces the orbitals to overlap poorly ("bent bonds"), so the C–C bonds are weak and these small rings are very reactive (cyclopropane forms explosive mixtures with air and can open its ring). Cyclopentane (angle ≈ 108°) and cyclohexane (≈ 109.5° in the non-planar chair form) have nearly normal angles, good overlap and strong σ bonds, so they are stable.
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 5 / 6
Part 6
Part 6
- 📖
🔍 In-Depth Explanations, Deductions & Multi-Book Insights:
Chemistry Thanaweya Amma (2026/2027)
- Lesson 3 – Alkynes (Acetylene) and Cyclic Hydrocarbons
- Detailed Academic Lesson Overview:
- Alkynes contain a carbon-carbon triple bond (one σ and two weak π bonds, general formula CnH2n-2).
- Acetylene (ethyne) is synthesized in the lab and burns with a high-temperature oxy-acetylene flame (3000°C) used in welding.
🌳 Hierarchy Classification & Conceptual Roadmap
Alkynes and Cycloalkanes
├── 1. Acetylene (Ethyne – C2H2)
| Comparison aspect | Main idea | Keywords |
|---|---|---|
| │ ├── Laboratory Preparation | Dropping water on Calcium Carbide (CaC2 + 2 H2O → C2H2 + Ca(OH)2) | DroppingwaterCalciumCarbide |
| │ ├── Industrial | Thermal quenching of Methane (2 CH4 at 1500°C rapid cool → C2H2 + 3 H2) | ThermalquenchingMethane1500 |
| • | │ └── Combustion | Combustion |
| │ ├── Limited O2 | Smoky flame due to unburned carbon | Smokyflameunburnedcarbon |
| │ └── Abundant O2 | Oxy-acetylene flame (3000°C) for cutting and welding metals | acetyleneflame3000cutting |
| • | ├── 2. Addition Reactions of Ethyne (Occurs in two sequential steps due to 2 π bonds) | AdditionReactionsEthyneOccurs |
| │ ├── Halogenation |
| C2H2tetrabromoethane |
| │ ├── Hydrohalogenation |
| C2H2Vinylbromidedibromoethane |
| │ └── Catalytic Hydration | C2H2 + H2O (40% H2SO4 / 1% HgSO4 at 60°C) → Acetaldehyde (CH3CHO) | C2H2H2SO4HgSO4Acetaldehyde |
| • |
| CycloalkanesGeneralformulaCnH2n |
| ├── Cyclopropane (bond angle 60°) and Cyclobutane (90°) | Unstable and highly active due to poor orbital overlap | Unstablehighlyactivepoor |
| • | └── Cyclopentane (108°) and Cyclohexane (109.5°): Completely stable due to tetrahedral angles | CyclopentaneCyclohexaneCompletelystable |
| • | 📋 Master Teacher's Blackboard Rules & Exam Secrets | MasterTeacherBlackboardRules |
| RULE 1 |
| Additionacetylenestepobeys |
| RULE 2 |
| Catalytichydrationethyneinitially |
| RULE 3 |
| Cyclopropaneisomerpropeneboth |
| 📊 Detailed Comparison Matrix | Ring Strain and Stability Comparison in Cycloalkanes | RingStrainStabilityCycloalkanes |
| Compound | Ring Bond Angle | Orbital Overlap Quality | Chemical Activity / Stability |
|---|---|---|---|
| Cyclopropane (C3H6) | 60° | Extremely weak overlap | Extremely active / flammable gas |
| Cyclobutane (C4H8) | 90° | Weak overlap | Active / burns easily |
| Cyclopentane (C5H10) | 108° | Strong orbital overlap | Stable non-reactive ring |
| Cyclohexane (C6H12) | 109.5° (Chair/Boat) | Ideal tetrahedral overlap | Highly stable / mimics straight alkanes |
Lesson 3: Alkynes (Acetylene) and Cyclic Hydrocarbons · 6 / 6
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