AQA A Level Chemistry Practice Questions and Answers

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