OCR A-Level Chemistry Unified chemistry (03), June 2025
Every question from OCR A-Level Chemistry Unified chemistry (03), June 2025 (H432): 6 questions, 70 marks, each with its mark scheme and topic.
- Question 1 8 marks
Deduce subatomic particle numbers and isotopic molecular ion peak origins with relative abundances for bromine, and predict proton NMR peaks and splitting patterns for two dibromoalkanes.
Module 2: Foundations in chemistry · Module 4: Core organic chemistry · Module 6: Organic chemistry and analysis · 2.1 Atoms and reactions · 4.2 Alcohols, haloalkanes and analysis · 6.3 Analysis
- Question 2 14 marks
Draw skeletal structures, perform mole and particle calculations, explain phenol acidity compared to carboxylic acids, and calculate the pH of a diluted barium hydroxide solution.
Module 2: Foundations in chemistry · Module 4: Core organic chemistry · Module 5: Physical chemistry and transition elements · Module 6: Organic chemistry and analysis · 2.1 Atoms and reactions · 4.1 Basic concepts and hydrocarbons · 4.2 Alcohols, haloalkanes and analysis · 5.1 Rates, equilibrium and pH · 6.1 Aromatic compounds, carbonyls and acids
- Question 3 11 marks
Explain the conditions for maximum equilibrium yield and calculate [H₂] using Kc, then determine orders of reaction, rate equation, rate constant, and deduce mechanism steps from experimental rate data.
Module 5: Physical chemistry and transition elements · Module 3: Periodic table and energy · 5.1 Rates, equilibrium and pH · 3.2 Physical chemistry
- Question 4 15 marks
Identify reactions and equations involving sulfate(IV) ions, and determine formulas, structures, and stereoisomers of a nickel(II) amino acid complex.
Module 2: Foundations in chemistry · Module 3: Periodic table and energy · Module 5: Physical chemistry and transition elements · Module 6: Organic chemistry and analysis · 2.1 Atoms and reactions · 3.1 The periodic table · 5.3 Transition elements · 6.2 Nitrogen compounds, polymers and synthesis
- Question 5 16 marks
Calculate the mass of reducing agent and percentage yield for an ester reduction, outline the mechanism with curly arrows, draw a dot-and-cross diagram for NaBH4, and determine cell potential and half-equation for a borohydride fuel cell.
Module 2: Foundations in chemistry · Module 4: Core organic chemistry · Module 5: Physical chemistry and transition elements · Module 6: Organic chemistry and analysis · 2.1 Atoms and reactions · 2.2 Electrons, bonding and structure · 4.1 Basic concepts and hydrocarbons · 4.2 Alcohols, haloalkanes and analysis · 5.2 Energy · 6.1 Aromatic compounds, carbonyls and acids
- Question 6 6 marks
Calculate the enthalpy change of reaction for the decomposition of sodium hydrogencarbonate using experimental calorimetry data for sodium carbonate reacting with nitric acid and an enthalpy cycle.
Module 1: Development of practical skills in chemistry · Module 2: Foundations in chemistry · Module 3: Periodic table and energy · Practical Activity Groups · 1.1 Practical skills assessed in a written examination · 2.1 Atoms and reactions · 3.2 Physical chemistry · PAG 3: Enthalpy determination