OR Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12 Not average mass of 1 molecule Allow the wording Average mass of 1 atom of an element compared to 1/12 mass atom of 12C (or mass 1/12 atom of 12C) Allow if moles of atoms on both lines Accept answer in words Can have top line × 12 instead of bottom line ÷12 If mixed, max = 1 Relative (ii) Mean /average mass of a molecule/entity/formula 1 Molecular Mass 1/12th mass of atom of 12C [Not 1/12th mass of molecule of 12C] (mark independently) 1 OR Mass of 1 mole of molecules/entities (1) 1/12thmass of 1 mole of 12C (1) OR Average mass of a molecule/entity (1) Relative to the mass of a 12C atom taken as 12 / 12.000 (1) (Mean/average = stated or explained) (mass = stated or explained) (Penalise once only) ‘weight’ (Ignore mass of 12C) ‘average ‘ (Do not allow of average molecule) ‘mass Standard Enthalpy change when 1 mol of a substance Enthalpy of (or compound) (QL mark) 1 Combustion is (completely) burned in oxygen (or reacted in excess oxygen) 1 at 298 K and 100 kPa (or under standard conditions) 1 Standard (Enthalpy change) when 1 mol (1) of a compound is formed Enthalpy of from its constituent elements (1) in their standard states (1) Formation Allow energy or heat, Ignore evolved or absorbed Mark each point independently (b)
OR Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12 Not average mass of 1 molecule Allow the wording Average mass of 1 atom of an element compared to 1/12 mass atom of 12C (or mass 1/12 atom of 12C) Allow if moles of atoms on both lines Accept answer in words Can have top line × 12 instead of bottom line ÷12 If mixed, max = 1 Relative Molecular Mass (ii) Mean /average mass of a molecule/entity/formula 1 1/12th mass of atom of 12C [Not 1/12th mass of molecule of 12C] (mark independently) 1 OR Mass of 1 mole of molecules/entities (1) 1/12thmass of 1 mole of 12C (1) OR Average mass of a molecule/entity (1) Relative to the mass of a 12C atom taken as 12 / 12.000 (1) (Mean/average = stated or explained) (mass = stated or explained) (Penalise ‘weight’ once only) (Ignore ‘average ‘ mass of 12C) (Do not allow ‘mass of average molecule) Standard Enthalpy of Combustion Enthalpy change when 1 mol of a substance (or compound) (QL mark) 1 is (completely) burned in oxygen (or reacted in excess oxygen) 1 at 298 K and 100 kPa (or under standard conditions) 1 Standard Enthalpy of Formation (Enthalpy change) when 1 mol (1) of a compound is formed from its constituent elements (1) in their standard states (1) Allow energy or heat, Ignore evolved or absorbed Mark each point independently (b)
as_chemistry_definitions_list_wt.docx