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IGCSE Chemistry Formula Sheet (0620)
IGCSE Chemistry Formula Sheet
Cambridge IGCSE Chemistry (0620) | Key Equations & Data
Based on official Cambridge syllabus 2026-2028
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Featured Formulas (8 key)
Across moles, concentration, yield & energetics#1Mass number = p + n
Atomic structure: protons + neutrons = mass number
Proton number identifies the element; neutrons + protons give mass.
#2n = m / M
Moles (Extended) from mass and molar mass
n = Moles (mol)
m = Mass (g)
M = Molar mass (g/mol)
m = Mass (g)
M = Molar mass (g/mol)
#3n = V / 24
Moles of gas (Extended) at room temperature and pressure
n = Moles (mol)
V = Volume (dm³)
24 = Molar gas volume at RTP (dm³/mol)
V = Volume (dm³)
24 = Molar gas volume at RTP (dm³/mol)
#4N = n × 6.02×10²³
Avogadro constant (Extended): particles from moles
N = Number of particles
n = Moles (mol)
6.02×10²³ = Avogadro constant
n = Moles (mol)
6.02×10²³ = Avogadro constant
#5c = n / V
Concentration in mol/dm³ (calculation Extended)
c = Concentration (mol/dm³)
n = Moles (mol)
V = Volume (dm³)
n = Moles (mol)
V = Volume (dm³)
#6% yield = (actual / theoretical) × 100
Percentage yield (Extended)
Actual = Mass produced (g)
Theoretical = Predicted mass (g)
Maximum 100%.
Theoretical = Predicted mass (g)
Maximum 100%.
#7% purity = (pure mass / total mass) × 100
Percentage purity (Extended)
Used in titration questions to find purity of an impure sample.
#8ΔH = Σ(broken) − Σ(made)
Enthalpy change (Extended) from bond energies
Use positive bond energies: total for bonds broken minus total for bonds made. Negative ΔH = exothermic.
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1. Atomic Structure
Mass number = p + n
Mass number = protons + neutrons
Also called nucleon number
Found at top left of element symbol
Also called nucleon number
Found at top left of element symbol
Proton number = protons
Atomic number = number of protons = number of electrons (in neutral atom)
Determines element identity
Found at bottom left of element symbol
Determines element identity
Found at bottom left of element symbol
Mᵣ = sum of Aᵣ
Relative molecular mass = relative atomic masses added up
Called relative formula mass for ionic compounds
Example: Mᵣ of H₂O = (2×1) + 16 = 18
Called relative formula mass for ionic compounds
Example: Mᵣ of H₂O = (2×1) + 16 = 18
Subatomic Particles:
| Particle | Relative Mass | Relative Charge | Location |
|---|---|---|---|
| Proton | 1 | +1 | Nucleus |
| Neutron | 1 | 0 | Nucleus |
| Electron | 1/1840 (≈0) | -1 | Shells |
2. Mole Calculations (Extended)
n = m / M
Moles = mass / molar mass
n = Amount of substance (mol)
m = Mass (g)
M = Molar mass (g/mol)
Tip: "Number of moles = grams divided by Mr"
n = Amount of substance (mol)
m = Mass (g)
M = Molar mass (g/mol)
Tip: "Number of moles = grams divided by Mr"
n = V / 24
Moles of gas = volume / molar gas volume
n = Amount of substance (mol)
V = Volume (dm³)
24 = Molar gas volume at RTP (dm³/mol)
Tip: 24 dm³ = 24000 cm³ at room temperature and pressure
n = Amount of substance (mol)
V = Volume (dm³)
24 = Molar gas volume at RTP (dm³/mol)
Tip: 24 dm³ = 24000 cm³ at room temperature and pressure
Particles = n × 6.02×10²³
Number of particles = moles × Avogadro constant
6.02 × 10²³ = Avogadro constant (particles/mol)
1 mole of any substance contains 6.02 × 10²³ particles
6.02 × 10²³ = Avogadro constant (particles/mol)
1 mole of any substance contains 6.02 × 10²³ particles
Aᵣ = Σ(mass × %)/100
Relative atomic mass from isotope abundances
Aᵣ = Relative atomic mass
Multiply each isotope mass by its percentage, sum and divide by 100
Aᵣ = Relative atomic mass
Multiply each isotope mass by its percentage, sum and divide by 100
Ratio of mass / Aᵣ
Empirical formula (Extended) = simplest whole-number ratio of atoms or ions
Find moles of each element, then divide by the smallest
Molecular formula: scale up to match Mᵣ
Find moles of each element, then divide by the smallest
Molecular formula: scale up to match Mᵣ
3. Concentration
Measured in g/dm³ or mol/dm³
c = n / V
Concentration in mol/dm³ (Extended) = moles / volume
c = Concentration (mol/dm³)
n = Amount of substance (mol)
V = Volume (dm³)
Tip: 1 dm³ = 1000 cm³ = 1 litre
c = Concentration (mol/dm³)
n = Amount of substance (mol)
V = Volume (dm³)
Tip: 1 dm³ = 1000 cm³ = 1 litre
c = m / V
Concentration in g/dm³ (Extended) = mass / volume
c = Concentration (g/dm³)
m = Mass of solute (g)
V = Volume of solution (dm³)
c = Concentration (g/dm³)
m = Mass of solute (g)
V = Volume of solution (dm³)
g/dm³ = mol/dm³ × Mᵣ
Converting concentration units (Extended)
To convert mol/dm³ to g/dm³: multiply by Mᵣ
To convert g/dm³ to mol/dm³: divide by Mᵣ
To convert mol/dm³ to g/dm³: multiply by Mᵣ
To convert g/dm³ to mol/dm³: divide by Mᵣ
4. Percentage Calculations (Extended)
% yield = (actual/theoretical) × 100
Percentage yield = (actual yield / theoretical yield) × 100
Actual yield = What you actually get (g)
Theoretical yield = What you should get (g)
Maximum 100%
Actual yield = What you actually get (g)
Theoretical yield = What you should get (g)
Maximum 100%
% purity = (pure/total) × 100
Percentage purity = (mass of pure substance / total mass) × 100
Used when sample contains impurities
100% purity means no impurities
Used when sample contains impurities
100% purity means no impurities
% by mass = (element/compound) × 100
Percentage composition = (mass of element / mass of compound) × 100
Use: (Aᵣ × number of atoms) / Mᵣ × 100
Example: % of O in H₂O = (16×1)/(18) × 100 = 88.9%
Use: (Aᵣ × number of atoms) / Mᵣ × 100
Example: % of O in H₂O = (16×1)/(18) × 100 = 88.9%
5. Energy & Enthalpy (Core + Extended)
ΔH = Σ(broken) - Σ(made)
Enthalpy change (Extended) = bonds broken - bonds made
ΔH = Enthalpy change (kJ/mol)
Σ(broken) = Sum of bond energies broken
Σ(made) = Sum of bond energies formed
Tip: Breaking bonds is endothermic, making bonds is exothermic. Use both totals as positive numbers
ΔH = Enthalpy change (kJ/mol)
Σ(broken) = Sum of bond energies broken
Σ(made) = Sum of bond energies formed
Tip: Breaking bonds is endothermic, making bonds is exothermic. Use both totals as positive numbers
Key Definitions:
- Exothermic: Thermal energy released to the surroundings, so their temperature rises. ΔH negative (Extended)
- Endothermic: Thermal energy taken in from the surroundings, so their temperature falls. ΔH positive (Extended)
- Activation energy, Eₐ (Extended): Minimum energy colliding particles need in order to react
6. Chromatography (Extended)
Rf = substance / solvent
Retention factor = distance by substance / distance by solvent
Rf = Retention factor (no unit, 0 to 1)
Measured from the baseline (pencil line)
Same substance = same Rf value (under same conditions)
Rf = Retention factor (no unit, 0 to 1)
Measured from the baseline (pencil line)
Same substance = same Rf value (under same conditions)
7. Reactivity Series
Order (most to least reactive):
K - Potassium
Na - Sodium
Ca - Calcium
Mg - Magnesium
Al - Aluminium
C - Carbon
Zn - Zinc
Fe - Iron
H - Hydrogen
Cu - Copper
Ag - Silver
Au - Gold
Mnemonic: "Please Send Charlie's Monkeys And Cute Zebras In Horrible Cages Securely Guarded"
Carbon and Hydrogen are reference points, not metals
Iron in the Blast Furnace (symbol equations Extended):
- Coke burns: C + O₂ → CO₂
- Carbon monoxide forms: C + CO₂ → 2CO
- Iron(III) oxide is reduced: Fe₂O₃ + 3CO → 2Fe + 3CO₂
- Limestone decomposes: CaCO₃ → CaO + CO₂
- Slag forms: CaO + SiO₂ → CaSiO₃
Aluminium by Electrolysis (half-equations Extended):
- Cathode: Al³⁺ + 3e⁻ → Al
- Anode: 2O²⁻ → O₂ + 4e⁻
8. Electrochemistry
Electrolysis Rules:
| Electrode | Charge | Ions Attracted (Extended) | Products |
|---|---|---|---|
| Cathode | Negative (-) | Cations (+) | Metals or H₂ |
| Anode | Positive (+) | Anions (-) | Non-metals (not H₂) |
Products with Inert Electrodes:
| Electrolyte | Cathode | Anode |
|---|---|---|
| Molten lead(II) bromide | Lead | Bromine |
| Concentrated aqueous sodium chloride | Hydrogen | Chlorine |
| Dilute sulfuric acid | Hydrogen | Oxygen |
At the Cathode, Reduction (Extended):
- Metal ions gain electrons: M⁺ + e⁻ → M
- In aqueous solution, if metal is above hydrogen in reactivity series → H₂ forms instead
- Hydrogen forms: 2H⁺ + 2e⁻ → H₂
At the Anode, Oxidation (Extended):
- Non-metal ions lose electrons: 2Cl⁻ → Cl₂ + 2e⁻
- Concentrated halide solutions → halogen forms
- Dilute solutions, including dilute halides → O₂ forms: 4OH⁻ → O₂ + 2H₂O + 4e⁻
Aqueous Copper(II) Sulfate (Extended):
- Copper electrodes, anode: Cu → Cu²⁺ + 2e⁻
- Copper electrodes, cathode: Cu²⁺ + 2e⁻ → Cu
- Copper electrodes, electrolyte: Blue colour does not change
- Carbon electrodes: O₂ forms at the anode (learn the cathode product and observations)
Oxidation Number Rules (Extended):
- Uncombined element: 0
- Monatomic ion: same as its charge
- Numbers in a compound add up to 0
- Numbers in an ion add up to the charge on the ion
9. Acids, Bases & Salts
H⁺(aq) + OH⁻(aq) → H₂O(l)
Neutralisation - ionic equation
Acid + Alkali → Salt + Water
Hydrogen ions react with hydroxide ions
Acid + Alkali → Salt + Water
Hydrogen ions react with hydroxide ions
HCl(aq) → H⁺(aq) + Cl⁻(aq)
Strong acid (Extended) - fully dissociated in water
Example: hydrochloric acid
Example: hydrochloric acid
CH₃COOH(aq) ⇌ H⁺(aq) + CH₃COO⁻(aq)
Weak acid (Extended) - partly dissociated in water
Example: ethanoic acid
Example: ethanoic acid
Key Acid and Base Reactions:
- Acid + Metal → Salt + Hydrogen
- Acid + Base → Salt + Water
- Acid + Carbonate → Salt + Water + CO₂
- Base + Ammonium salt → Salt + Water + Ammonia
pH Scale:
0-6 Acidic 7 Neutral 8-14 Alkaline
Indicators:
- Litmus: Red litmus turns blue in alkali (learn its colour in acid)
- Thymolphthalein: Colourless in acid, blue in alkali
- Methyl orange: Red or pink in acid, yellow in alkali
Solubility Rules:
| Salts | Rule | Exceptions |
|---|---|---|
| Sodium, potassium, ammonium | Soluble | — |
| Nitrates | Soluble | — |
| Chlorides | Soluble | Lead, silver |
| Sulfates | Soluble | Barium, calcium, lead |
| Carbonates | Insoluble | Sodium, potassium, ammonium |
| Hydroxides | Insoluble | Sodium, potassium, ammonium, calcium (partially) |
Water of Crystallisation (Extended):
Water molecules held in hydrated crystals: CuSO₄•5H₂O, CoCl₂•6H₂O
10. Organic Chemistry
Homologous Series General Formulae:
| Series | Formula | Functional Group | Example |
|---|---|---|---|
| Alkanes | CₙH₂ₙ₊₂ | — | CH₄, C₂H₆ |
| Alkenes | CₙH₂ₙ | C=C (double) | C₂H₄, C₃H₆ |
| Alcohols | CₙH₂ₙ₊₁OH | -OH | CH₃OH, C₂H₅OH |
| Carboxylic acids | CₙH₂ₙ₊₁COOH | -COOH | HCOOH, CH₃COOH |
Key Reactions:
- Complete combustion: Hydrocarbon + O₂ → CO₂ + H₂O
- Fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (aqueous glucose, 25-35°C, yeast, no oxygen)
- Ethanol from ethene: Ethene + Steam → Ethanol (300°C, 6000 kPa / 60 atm, acid catalyst)
- Esterification (Extended): Alcohol + Carboxylic acid → Ester + Water (acid catalyst)
- Cracking: Large alkane → Alkene + Hydrogen or smaller alkane (high temperature, catalyst)
11. Chemical Tests
Gas Tests:
| Gas | Test | Result |
|---|---|---|
| Hydrogen (H₂) | Lighted splint | Pops |
| Oxygen (O₂) | Glowing splint | Relights |
| Carbon dioxide (CO₂) | Limewater | Turns milky/cloudy |
| Chlorine (Cl₂) | Damp litmus paper | Bleaches |
| Ammonia (NH₃) | Damp red litmus | Turns blue |
| Sulfur dioxide (SO₂) | Acidified aqueous KMnO₄ | Purple to colourless |
Ion Tests:
| Ion | Test | Result |
|---|---|---|
| Carbonate (CO₃²⁻) | Add dilute acid, then test for CO₂ | Fizzes, CO₂ produced |
| Chloride (Cl⁻) | Dilute HNO₃ + AgNO₃ | White precipitate |
| Bromide (Br⁻) | Dilute HNO₃ + AgNO₃ | Cream precipitate |
| Iodide (I⁻) | Dilute HNO₃ + AgNO₃ | Yellow precipitate |
| Sulfate (SO₄²⁻) | Dilute HNO₃ + Ba(NO₃)₂ | White precipitate |
| Nitrate (NO₃⁻) | Aqueous NaOH, then aluminium foil, warm carefully | Ammonia produced |
| Sulfite (SO₃²⁻) | A little acidified aqueous KMnO₄ | Purple to colourless |
Aqueous Cation Tests:
| Cation | Aqueous NaOH | Aqueous NH₃ |
|---|---|---|
| Aluminium (Al³⁺) | White precipitate, soluble in excess (colourless solution) | White precipitate, insoluble in excess |
| Ammonium (NH₄⁺) | Ammonia produced on warming | — |
| Calcium (Ca²⁺) | White precipitate, insoluble in excess | No precipitate or very slight white precipitate |
| Chromium(III) (Cr³⁺) | Green precipitate, soluble in excess | Green precipitate, insoluble in excess |
| Copper(II) (Cu²⁺) | Light blue precipitate, insoluble in excess | Light blue precipitate, soluble in excess (dark blue solution) |
| Iron(II) (Fe²⁺) | Green precipitate, insoluble in excess, turns brown near surface on standing | Green precipitate, insoluble in excess, turns brown near surface on standing |
| Iron(III) (Fe³⁺) | Red-brown precipitate, insoluble in excess | Red-brown precipitate, insoluble in excess |
| Zinc (Zn²⁺) | White precipitate, soluble in excess (colourless solution) | White precipitate, soluble in excess (colourless solution) |
Flame Tests:
| Cation | Flame Colour |
|---|---|
| Lithium (Li⁺) | Red |
| Sodium (Na⁺) | Yellow |
| Potassium (K⁺) | Lilac |
| Calcium (Ca²⁺) | Orange-red |
| Barium (Ba²⁺) | Light green |
| Copper(II) (Cu²⁺) | Blue-green |
Water Tests:
- Presence: Anhydrous cobalt(II) chloride turns from blue to pink
- Presence: Anhydrous copper(II) sulfate turns from white to blue
- Purity: Check the melting point and boiling point
Test for Unsaturation:
- Aqueous bromine: Brown to colourless with unsaturated hydrocarbons, no change with saturated hydrocarbons
12. Key Numbers & Constants
| Avogadro constant (Extended) | 6.02 × 10²³ /mol |
| Molar gas volume at RTP (Extended) | 24 dm³/mol |
| 1 dm³ | = 1000 cm³ = 1 litre |
| Water boiling point | 100°C |
| Water freezing point | 0°C |
| Clean, dry air | about 78% N₂, 21% O₂, rest noble gases + CO₂ |
Industrial Processes (Extended):
- Haber: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
- 450°C, 20 000 kPa / 200 atm, iron catalyst. H₂ from methane, N₂ from air
- Contact: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
- 450°C, 200 kPa / 2 atm, vanadium(V) oxide catalyst. SO₂ from burning sulfur or roasting sulfide ores, O₂ from air
Air & Climate:
- Photosynthesis: Carbon dioxide + Water → Glucose + Oxygen
- Photosynthesis (Extended): 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Catalytic converter (Extended): 2CO + 2NO → 2CO₂ + N₂
More Resources
LumiExams.com | Cambridge IGCSE Chemistry (0620) | Syllabus 2026-2028
Frequently Asked Questions
What formulas do I need for IGCSE Chemistry?
Extended candidates need key IGCSE Chemistry formulas including moles = mass/Mr, concentration = moles/volume, percentage yield, and Rf value for chromatography. All candidates also need to know the reactivity series, electrochemistry rules, and common chemical tests.
Is a formula sheet provided in IGCSE Chemistry exams?
The syllabus lists no formula sheet for the exams. It prints the periodic table and says qualitative analysis notes are provided for Papers 5 and 6, but the reactivity series must be learned, and Extended candidates need to memorize formulas for mole calculations, concentration, and percentages. Our formula sheet gathers key equations and data for revision.
What topics are covered in this Chemistry formula sheet?
This formula sheet covers 12 topics: Atomic Structure, Mole Calculations, Concentration, Percentage Calculations, Energy & Enthalpy, Chromatography, Reactivity Series, Electrochemistry, Acids/Bases/Salts, Organic Chemistry, Chemical Tests, and Key Constants.
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