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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 2023-2025
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Featured Formulas (8 core)
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 from mass and relative molecular mass
n = Moles (mol)
m = Mass (g)
M = Relative mass (g/mol)
m = Mass (g)
M = Relative mass (g/mol)
#3n = V / 24
Moles of gas 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's law: 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
c = Concentration (mol/dm³)
n = Moles (mol)
V = Volume (dm³)
n = Moles (mol)
V = Volume (dm³)
#6% yield = (actual / theoretical) × 100
Percentage yield
Actual = Mass produced (g)
Theoretical = Predicted mass (g)
Always ≤ 100%.
Theoretical = Predicted mass (g)
Always ≤ 100%.
#7% purity = (pure mass / total mass) × 100
Percentage purity
Used in titration questions to find purity of an impure sample.
#8ΔH = Σ(broken) − Σ(made)
Enthalpy change from bond energies
Bonds broken (endo, +ve) minus bonds made (exo, −ve). 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 = electrons
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
Subatomic Particles:
| Particle | Relative Mass | Relative Charge | Location |
|---|---|---|---|
| Proton | 1 | +1 | Nucleus |
| Neutron | 1 | 0 | Nucleus |
| Electron | 1/1836 (≈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
3. Concentration (Extended)
c = n / V
Concentration (mol/dm³) = 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 (g/dm³) = 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
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)
Always less than 100% in real experiments
Actual yield = What you actually get (g)
Theoretical yield = What you should get (g)
Always less than 100% in real experiments
% 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 (Extended)
ΔH = Σ(broken) - Σ(made)
Enthalpy change = 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 = endothermic (+), Making bonds = exothermic (-)
ΔH = Enthalpy change (kJ/mol)
Σ(broken) = Sum of bond energies broken
Σ(made) = Sum of bond energies formed
Tip: Breaking bonds = endothermic (+), Making bonds = exothermic (-)
Key Definitions:
- Exothermic: ΔH negative, releases energy, temperature increases
- Endothermic: ΔH positive, absorbs energy, temperature decreases
- Activation energy (Eₐ): Minimum energy needed for reaction to occur
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 Zebras In Horrible Cages Securely Guarded"
Carbon and Hydrogen are reference points, not metals
8. Electrochemistry
Electrolysis Rules:
| Electrode | Charge | Ions Attracted | Products |
|---|---|---|---|
| Cathode | Negative (-) | Cations (+) | Metals or H₂ |
| Anode | Positive (+) | Anions (-) | Non-metals (not H₂) |
At the Cathode (Reduction):
- Metal ions gain electrons: M⁺ + e⁻ → M
- If metal is above hydrogen in reactivity series → H₂ forms instead
At the Anode (Oxidation):
- Non-metal ions lose electrons: 2Cl⁻ → Cl₂ + 2e⁻
- Dilute solutions with no halide → O₂ forms
9. Acids, Bases & Salts
H⁺ + OH⁻ → H₂O
Neutralisation - ionic equation
Acid + Alkali → Salt + Water
Hydrogen ions react with hydroxide ions
Acid + Alkali → Salt + Water
Hydrogen ions react with hydroxide ions
Key Acid Reactions:
- Acid + Metal → Salt + Hydrogen
- Acid + Base → Salt + Water
- Acid + Carbonate → Salt + Water + CO₂
pH Scale:
0-6 Acidic 7 Neutral 8-14 Alkaline
10. Organic Chemistry
Homologous Series General Formulae:
| Series | Formula | Functional Group | Example |
|---|---|---|---|
| Alkanes | CₙH₂ₙ₊₂ | C-C (single) | CH₄, C₂H₆ |
| Alkenes | CₙH₂ₙ | C=C (double) | C₂H₄, C₃H₆ |
| Alcohols | CₙH₂ₙ₊₁OH | -OH | CH₃OH, C₂H₅OH |
| Carboxylic acids | CₙH₂ₙ₊₁COOH | -COOH | HCOOH, CH₃COOH |
Key Reactions:
- Combustion: Hydrocarbon + O₂ → CO₂ + H₂O
- Fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
- Esterification: Alcohol + Acid → Ester + Water
- Cracking: Large alkane → Smaller alkane + Alkene
11. Chemical Tests
Gas Tests:
| Gas | Test | Result |
|---|---|---|
| Hydrogen (H₂) | Burning splint | Squeaky pop |
| Oxygen (O₂) | Glowing splint | Relights |
| Carbon dioxide (CO₂) | Limewater | Turns milky/cloudy |
| Chlorine (Cl₂) | Damp litmus paper | Bleaches white |
| Ammonia (NH₃) | Damp red litmus | Turns blue |
Ion Tests:
| Ion | Test | Result |
|---|---|---|
| Carbonate (CO₃²⁻) | Add dilute acid | 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 |
12. Key Numbers & Constants
| Avogadro constant | 6.02 × 10²³ /mol |
| Molar gas volume (RTP) | 24 dm³/mol |
| 1 dm³ | = 1000 cm³ = 1 litre |
| Room temperature | 25°C (298 K) |
| Standard pressure | 1 atm = 101 kPa |
| Water boiling point | 100°C (373 K) |
| Water freezing point | 0°C (273 K) |
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LumiExams.com | Cambridge IGCSE Chemistry (0620) | Syllabus 2023-2025
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