AQA A Level Chemistry
2026 | Comprehensive
Study Guide, Practice
Questions, Answers,
Practicals & Exam Review |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
, Relative atomic mass The average mass of an atom of an element, relative to 1/12th of the mass of an
atom of Carbon-12
Relative molecular mass Average mass of a molecule compared to 1/12th of the mass of a carbon-12 atom
The Avogradro constant the number of particles in a mole
ideal gas equation pV = nRT
empirical formula the simplest whole number ratio of atoms of each element in a compound
percentage atom economy (Mass of desired product/total mass of reactants) x 100
ionic bonding the electrostatic attraction between oppositely charged ions in a lattice
covalent bond a shared pair of electrons between non-metal elements
co-ordinate bond a shared pair of electrons where both electrons are supplied by one atom
repulsion in shapes of molecules Lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair
electronegativity the power of an atom to attract the pair of electrons in a covalent bond
hess' law Total enthalpy change for a reaction is independent of the route chosen
mean bond enthalpy The energy required to break a covalent bond into gaseous atoms averaged over
different molecules
Bonds broken - bonds made
activation energy The minimum amount of energy needed to start a chemical reaction
catalyst A substance that increases the rate of a chemical reaction without being changed
by providing an alternative reaction pathway by lowering activation energy
2026 | Comprehensive
Study Guide, Practice
Questions, Answers,
Practicals & Exam Review |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
, Relative atomic mass The average mass of an atom of an element, relative to 1/12th of the mass of an
atom of Carbon-12
Relative molecular mass Average mass of a molecule compared to 1/12th of the mass of a carbon-12 atom
The Avogradro constant the number of particles in a mole
ideal gas equation pV = nRT
empirical formula the simplest whole number ratio of atoms of each element in a compound
percentage atom economy (Mass of desired product/total mass of reactants) x 100
ionic bonding the electrostatic attraction between oppositely charged ions in a lattice
covalent bond a shared pair of electrons between non-metal elements
co-ordinate bond a shared pair of electrons where both electrons are supplied by one atom
repulsion in shapes of molecules Lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair
electronegativity the power of an atom to attract the pair of electrons in a covalent bond
hess' law Total enthalpy change for a reaction is independent of the route chosen
mean bond enthalpy The energy required to break a covalent bond into gaseous atoms averaged over
different molecules
Bonds broken - bonds made
activation energy The minimum amount of energy needed to start a chemical reaction
catalyst A substance that increases the rate of a chemical reaction without being changed
by providing an alternative reaction pathway by lowering activation energy
