CAIE IGCSE Chemistry 0620/42 May/June 2024 – Model Answers: worked solutions on gas ID, redox/displacement, the Haber process (conditions/equilibrium/enthalpy), esterification & pH, sulfur isotopes/oxidation states, ionic bonding, and qualitative tests.  Includes balanced equations, calculations, and clear explanations for photosynthesis/fermentation and ethene hydration (300 °C, 60 atm, acid) for quick self-marking revision.