IGCSE CHEM FORMULAE SHEET-
General Chemistry
● Moles: moles = mass (g) ÷ molar mass (g/mol)
● Concentration (mol/dm³): C = n ÷ V
● Gas volume at RTP: 1 mole = 24 dm³
● Relative formula mass: Mr = sum of Ar of atoms
● Avogadro constant: 6.022 × 10²³ particles/mole
● Percentage composition: % element = (Ar × number of atoms ÷ Mr) × 100
Stoichiometry
● Balanced equation mole ratios for calculation
● Percentage yield: % yield = (actual ÷ theoretical) × 100
● Atom economy: Atom economy = (Mr of desired product ÷ Mr of all products) × 100
● Limiting reagent: Use mole ratio to identify limiting reactant
Acids, Bases & pH
● pH = –log[H⁺]
● [H⁺] = 10⁻ᵖᴴ
● Strong acid: complete dissociation
● Weak acid: Ka = [H⁺][A⁻] ÷ [HA]
● % ionisation = ([H⁺] ÷ [HA]) × 100
Energetics
● Heat energy: Q = mcΔT
● Enthalpy change: ΔH = H_products – H_reactants
● Bond enthalpy: ΔH = bonds broken – bonds formed
General Chemistry
● Moles: moles = mass (g) ÷ molar mass (g/mol)
● Concentration (mol/dm³): C = n ÷ V
● Gas volume at RTP: 1 mole = 24 dm³
● Relative formula mass: Mr = sum of Ar of atoms
● Avogadro constant: 6.022 × 10²³ particles/mole
● Percentage composition: % element = (Ar × number of atoms ÷ Mr) × 100
Stoichiometry
● Balanced equation mole ratios for calculation
● Percentage yield: % yield = (actual ÷ theoretical) × 100
● Atom economy: Atom economy = (Mr of desired product ÷ Mr of all products) × 100
● Limiting reagent: Use mole ratio to identify limiting reactant
Acids, Bases & pH
● pH = –log[H⁺]
● [H⁺] = 10⁻ᵖᴴ
● Strong acid: complete dissociation
● Weak acid: Ka = [H⁺][A⁻] ÷ [HA]
● % ionisation = ([H⁺] ÷ [HA]) × 100
Energetics
● Heat energy: Q = mcΔT
● Enthalpy change: ΔH = H_products – H_reactants
● Bond enthalpy: ΔH = bonds broken – bonds formed
