Pearson Edexcel IAL Chemistry Past Papers & Mark Schemes

IAL Chemistry mechanism questions follow strict marking conventions. Curly arrows must originate from a lone pair or a bond — never from an atom symbol or a charge. They must point to the atom where the electrons end up or to the bond being formed. For nucleophilic substitution, show the lone pair on the nucleophile, the curly arrow attacking the electrophilic carbon, the simultaneous departure of the leaving group (SN2) or the prior formation of a carbocation (SN1). Each arrow carries a mark, so missing even one arrow typically costs a mark. Quantitative chemistry questions require systematic working. For moles calculations: write the equation, identify mole ratios, calculate moles from the information given (moles = mass/Mr, or moles = concentration × volume in dm³), use the ratio to find moles of the target substance, and convert to the required answer. For enthalpy calculations: state the formula (q = mcΔT), substitute with correct units (mass in g, c in J g⁻¹ K⁻¹, ΔT in K or °C), calculate, and convert to kJ mol⁻¹ by dividing by moles. Group chemistry and periodicity questions demand precision about trends and their explanations. Down Group 2: atomic radius increases (more electron shells), ionisation energy decreases (greater shielding, electrons further from nucleus), reactivity increases. Across Period 3: ionisation energy generally increases (increasing nuclear charge with constant shielding) but drops between Groups 2 and 3 (electron entering a higher-energy p sub-shell) and between Groups 5 and 6 (spin-pair repulsion in p⁴ configuration). For Unit 6's synoptic questions, prepare to apply knowledge from any unit to unfamiliar experimental scenarios. A question might present data from an electrochemistry experiment (Unit 5 content) but require you to calculate enthalpy changes (Unit 1) and suggest improvements to experimental methodology (Unit 3). Practise past Unit 6 papers specifically — the unfamiliar contexts reward flexible application of core principles.