9701/21/O/N/25 · Chemistry October/November 2025 Paper 21
4 questions, 60 marks. Each one links to its official mark scheme.
- Question 1 · 20 marks · Particles in the atom and atomic radius, Isotopes, Mass spectrometry, Electrons, energy levels and atomic orbitals, Oxidation and reduction, Oxidation numbers, Balancing redox equations, Intermolecular forces, Dynamic equilibrium, Le Chatelier's principle, Period 3 chlorides with water
- Question 2 · 11 marks · Period 3 physical properties, Particles in the atom and atomic radius, Oxidation numbers of oxides and chlorides, Explaining Period 3 trends, Period 3 oxides and hydroxides, Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds, Thermal decomposition
- Question 3 · 13 marks · Formulas, Structural isomerism, Characteristic organic reactions, Alkanes, Electrophilic addition, Hess’s law, Oxidising alkenes, Infrared spectroscopy
- Question 4 · 16 marks · Carboxylic acids, Making halogenoalkanes, Elimination, Making alkenes, Addition polymerisation, Cis/trans isomerism, Optical isomerism, Organic formulas and naming, Mass spectrometry
Questions and mark schemes from Cambridge International past papers. Paperstreak isn't affiliated with Cambridge.