Official June 2024 AQA A-LEVEL CHEMISTRY 7405/3
Paper 3
Relative atomic mass - ANSWER 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 - ANSWER Average mass of a molecule compared to
1/12th of the mass of a carbon-12 atom
The Avogradro constant - ANSWER the number of particles in a mole
ideal gas equation - ANSWER pV = nRT
empirical formula - ANSWER the simplest whole number ratio of atoms of each
element in a compound
percentage atom economy - ANSWER (Mass of desired product/total mass of
reactants) x 100
ionic bonding - ANSWER the electrostatic attraction between oppositely charged
ions in a lattice
covalent bond - ANSWER a shared pair of electrons between non-metal elements
co-ordinate bond - ANSWER a shared pair of electrons where both electrons are
supplied by one atom
repulsion in shapes of molecules - ANSWER Lone pair-lone pair > lone pair-bonding
pair > bonding pair-bonding pair
electronegativity - ANSWER the power of an atom to attract the pair of electrons in a
covalent bond
hess' law - ANSWER Total enthalpy change for a reaction is independent of the
route chosen
mean bond enthalpy - ANSWER The energy required to break a covalent bond into
gaseous atoms averaged over different molecules
Bonds broken - bonds made
activation energy - ANSWER The minimum amount of energy needed to start a
chemical reaction
catalyst - ANSWER A substance that increases the rate of a chemical reaction
without being changed by providing an alternative reaction pathway by lowering
activation energy
, Le Chatelier's principle - ANSWER When a system in dynamic equilibrium is
subjected to change, the position of equilibrium will shift to oppose the change.
oxidising agents - ANSWER electron acceptors
reducing agents - ANSWER electron donors
Enthalpy of formation - ANSWER Enthalpy change when one mole of a compound
is formed from its constituent elements under standard conditions in their standard
states
Enthalpy of atomization - ANSWER The energy required to produce one mole of
gaseous atoms from an element in its standard state
Electron affinity - ANSWER the enthaply change when one mole of gaseous atoms
forms one mole of -1 ions
Lattice enthalpy of formation - ANSWER Enthalpy change when one mole of a solid
ionic compound is formed from its constituent ions in the gas phase
Lattice enthalpy of dissociation - ANSWER Energy change when 1 mol of an ionic
lattice dissociates to its gaseous ions.
standard electrode potential - ANSWER 298K
100kPa
1.00moldm-3
Electrode reactions in lithium cell
(positive electrode) - ANSWER Li+ + CoO2 + e- → Li+[CoO2]-
Electrode reactions in lithium cell
(negative electrode) - ANSWER Li → Li+ + e-
Electrode reactions in hydrogen-oxygen fuel cell in acidic conditions
(positive electrode) - ANSWER 02 + 4H+ +4e- -> 2H20
Electrode reactions in hydrogen-oxygen fuel cell in acidic conditions
(negative electrode) - ANSWER H2 -> 2H+ + 2e-
Brosted- lowry Acid - ANSWER proton donor
Brosted- lowry base - ANSWER proton acceptor
weak acids - ANSWER partially dissociate in aqueous solution
what is an acidic buffer made of? - ANSWER weak acid and its salt
what is an basic buffer made of? - ANSWER weak base and its salt
Paper 3
Relative atomic mass - ANSWER 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 - ANSWER Average mass of a molecule compared to
1/12th of the mass of a carbon-12 atom
The Avogradro constant - ANSWER the number of particles in a mole
ideal gas equation - ANSWER pV = nRT
empirical formula - ANSWER the simplest whole number ratio of atoms of each
element in a compound
percentage atom economy - ANSWER (Mass of desired product/total mass of
reactants) x 100
ionic bonding - ANSWER the electrostatic attraction between oppositely charged
ions in a lattice
covalent bond - ANSWER a shared pair of electrons between non-metal elements
co-ordinate bond - ANSWER a shared pair of electrons where both electrons are
supplied by one atom
repulsion in shapes of molecules - ANSWER Lone pair-lone pair > lone pair-bonding
pair > bonding pair-bonding pair
electronegativity - ANSWER the power of an atom to attract the pair of electrons in a
covalent bond
hess' law - ANSWER Total enthalpy change for a reaction is independent of the
route chosen
mean bond enthalpy - ANSWER The energy required to break a covalent bond into
gaseous atoms averaged over different molecules
Bonds broken - bonds made
activation energy - ANSWER The minimum amount of energy needed to start a
chemical reaction
catalyst - ANSWER A substance that increases the rate of a chemical reaction
without being changed by providing an alternative reaction pathway by lowering
activation energy
, Le Chatelier's principle - ANSWER When a system in dynamic equilibrium is
subjected to change, the position of equilibrium will shift to oppose the change.
oxidising agents - ANSWER electron acceptors
reducing agents - ANSWER electron donors
Enthalpy of formation - ANSWER Enthalpy change when one mole of a compound
is formed from its constituent elements under standard conditions in their standard
states
Enthalpy of atomization - ANSWER The energy required to produce one mole of
gaseous atoms from an element in its standard state
Electron affinity - ANSWER the enthaply change when one mole of gaseous atoms
forms one mole of -1 ions
Lattice enthalpy of formation - ANSWER Enthalpy change when one mole of a solid
ionic compound is formed from its constituent ions in the gas phase
Lattice enthalpy of dissociation - ANSWER Energy change when 1 mol of an ionic
lattice dissociates to its gaseous ions.
standard electrode potential - ANSWER 298K
100kPa
1.00moldm-3
Electrode reactions in lithium cell
(positive electrode) - ANSWER Li+ + CoO2 + e- → Li+[CoO2]-
Electrode reactions in lithium cell
(negative electrode) - ANSWER Li → Li+ + e-
Electrode reactions in hydrogen-oxygen fuel cell in acidic conditions
(positive electrode) - ANSWER 02 + 4H+ +4e- -> 2H20
Electrode reactions in hydrogen-oxygen fuel cell in acidic conditions
(negative electrode) - ANSWER H2 -> 2H+ + 2e-
Brosted- lowry Acid - ANSWER proton donor
Brosted- lowry base - ANSWER proton acceptor
weak acids - ANSWER partially dissociate in aqueous solution
what is an acidic buffer made of? - ANSWER weak acid and its salt
what is an basic buffer made of? - ANSWER weak base and its salt
