C (Core Theory)

Examiner notes & key calculations

• Premature Rounding: A recurrent issue across both papers was candidates rounding their intermediate mole values too early (e.g., truncating 0.00409 0.00409 0.00409 mol of pentanol to 0.004 0.004 0.004 mol), which led to incorrect final answers. Students must retain full calculator values until the final calculation step.
• Incorrect Enthalpy Signs: In the pentanol energetics question, many students failed to include the negative sign for the exothermic reaction, despite the prompt explicitly asking to include a sign.
• Incomplete Chemical Test Descriptions: When describing tests, candidates often wrote down only the result (e.g., "squeaky pop") instead of the full procedure and observation (e.g., "introducing a burning splint to the gas, which burns with a squeaky pop").
• Imprecise Terminology: Students frequently confused intramolecular covalent bonds with weak intermolecular forces when explaining melting points, or referred to halogens displacing "chlorine" or "iodine" instead of "chloride" or "iodide" ions.