AQA A-level Chemistry paper 2 Questions & Correct Answers/ Graded A+

elative atomic mass (Ar) : Average mass of an atom compared with one twelth of the mass of an atom of carbon 12 Electronegativity : Power of an atom to attract the pair of electrons in a covalent bond Standard enthalpy of combustion : Enthalpy change when 1 mole of a substance burns completely in oxygen under standard conditions with all reactants and products being in their standard state Standard enthalpy of formation : Enthalpy change when 1 mole of a compound is formed from it's elements under standard conditions in their standard states Mean bond enthalpy 2 : The average energy needed to break a certain type of bond over a range of compounds Activation energy : Minimum energy required for colliding molecules to react Maxwell-Boltzmann distribution x and y axes : x: Energy y: fraction/number of molecules What happens to the Maxwell-Boltzmann curve when temperature increases : Moves down and to the right Rate of reaction : Rate at which product formed/reactant used up Order of reaction : Power to which the concentration of a species is raised in the rate equation 3 rearrange k=Ae^-Ea/Rt : lnk=-Ea/Rt+lnA Conditions for thermal cracking : High temperature and high pressure Products of thermal cracking : High % of alkenes Conditions for catalytic cracking : High temperature ,slight pressure and in the presence of a zeolite catalyst Products of catalytic cracking : Motor fuels and aromatic hydrocarbons Why do we crack alkanes? : Smaller alkanes/alkenes generally more useful than longer chain ones 4 Equation for complete combustion of al