IGCSE Resources
Revision and Formula Sheet
For Cambridge IGCSE
Chemistry (0620)
- by _peacegod.
Chemical Reactions
● Contact Process:
○ 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
○ Source of SO₂:
■ Burning sulfur in air
● S(s) + O₂(g) → SO₂(g)
■ Roasting sulfide ores such as Zinc blende (ZnS).
● 2ZnS(s) + 3O₂(g) → 2ZnO(s) + 2SO₂(g)
○ Conditions required:
■ 450 °C
■ 200k Pa / 2 atm
■ Vanadium (V) Oxide catalyst
● Haber Process
○ N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
○ Conditions required:
■ 450 °C
■ 20 000kPa / 200 atm
■ Iron catalyst
● Metals
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Acid + metal carbonate → salt + H₂O + CO₂
Acid + alkali → salt + H₂O(l)
Metal + acid → salt + H₂(g)
Metal + water → metal hydroxide + hydrogen
■ Only metals such as Potassium, Sodium and calcium react with
water. (Mg does too but slowly)
■ Rest of the metals react with steam to produce Metal oxide +
hydrogen gas
Acid + metal oxide → salt + H₂O(l)
Metal oxide/hydroxide + ammonium salt → salt + ammonia(g) + H₂O(l)
ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l)
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ZnO(s) + 2NaOH(aq) → Na₂ZnO₂(aq) + H₂O(l)
Zinc oxide + sodium hydroxide → sodium zincate + water
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Al₂O₃(s) + 2NaOH(aq) → 2NaAlO₂(aq) + H₂O(l)
Aluminium oxide + sodium hydroxide → sodium illuminate + water
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● Hydration (Alkene to Alkanol)
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Catalytic addition reaction of steam
Conditions required:
■ 300 °C
■ 6000kPa / 60 atm
■ (Acidified) Phosphoric (V) acid catalyst
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● Complete and Incomplete combustion
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When burned in a good supply of air the products are CO₂ and H₂O(g).
When burned in a limited supply of air the products are CO and H₂O(g).
● Hydrogenation
○ Conditions required:
■ 200°C.
■ Nickel catalyst.
● Bromination (Test for unsaturation)
○ Aqueous bromine turns colorless when reacted with an alkene.
○ Unsaturated compounds have molecules in which one or more
carbon–carbon bonds are not single bonds.
● Cracking
○ Conditions required:
■ 500°C
■ Alumina or Silica catalyst
○ Decane → octane + ethene
○ C₁₀H₂₂ → C₈H₁₈ + C₂H₄
○ Note:
■ Two or more alkenes and hydrogen will be formed.
■ Or an alkane and an alkene (both short chains).
● Oxidation (Ethanol to Ethanoic acid)
○ Conditions required:
■ (Acidified) Aqueous Potassium Manganate (VII)
■ KMnO₄ (aq)
● Substitution reaction with Chlorine
○ Photochemical reaction
■ The activation energy required to start the reaction is
provided by UV light (sun light).
■ Methane + chlorine → chloromethane + hydrogen chloride
■ CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g)
● Oxides of Nitrogen
○ N₂(g) + O₂ → 2NO(g)
○ 3NO₂(g) + H₂O(l) → 2HNO₃(aq) + NO(g)
● Photosynthesis
○ Carbon dioxide + water → glucose + oxygen
○ 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
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● Fermentation
○ Anaerobic respiration.
■ Takes place in the presence of yeast and in the absence
of oxygen.
○ Catalysed by enzymes in the yeast.
○ Temperature required: between 25 and 35 °C.
○ Aqueous glucose (enzymes)→ ethanol + carbon dioxide
○ C₆H₁₂O₆ (aq) → 2C₂H₅OH (aq) + 2CO₂ (g)
● Metals Extraction
○ the burning of carbon (coke) to provide heat and produce
carbon dioxide.
○ C + O₂ → CO₂
○ the reduction of carbon dioxide to carbon monoxide.
○ C + CO₂ → 2CO
○ the reduction of iron(III) oxide by carbon monoxide.
○ Fe2O₃ + 3CO → 2Fe + 3CO₂
○ the thermal decomposition of calcium carbonate /limestone to
produce calcium oxide.
○ CaCO₃ → CaO + CO₂
○ the formation of slag
○ CaO + SiO₂ → CaSiO₃ (Calcium Silicate)
○ Why is coke added ?
■ Coke releases heat.
■ Coke reduces iron(III) oxide.
■ Coke reacts with carbon dioxide to form carbon monoxide.
○ Role of cryolite
■ Acts as a solvent.
■ Improves conductivity.
■ Lowers the operating temperature.
○ Why do carbon anodes need to be replaced regularly ?
■ At high temperature, the oxygen reacts with the carbon in the
electrodes forming CO2. The carbon anodes then slowly burn
away and have to be replaced frequently.
○ The reactions at the electrodes:
■ Al³⁺(l) + 3e⁻ → Al(l)
■ 2O²⁻(l) → O₂(g) + 4e⁻
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