AQA Chemistry Paper 2 Review

This guide covers important topics for AQA Chemistry Paper 2, beneficial for both Higher and Foundation Tiers in combined science (Trilogy) and separate Chemistry.

Topics Overview

• Rates of Reaction
• Organic Chemistry
• Analysis
• Atmospheric Chemistry
• Resources

Rates of Reaction

• Definition: How quickly a reaction occurs, calculated as the change in quantity divided by time.
• Experiments:
  • Hydrochloric Acid & Sodium Thiosulfate: Reacting in a conical flask over a cross to observe turbidity.
  • Gas Syringe: Measures the volume of gas produced.
• Graphs: Plot quantity vs. time. Use a tangent for accurate rate calculations.
• Increasing Reaction Rate:
  • Increase concentration, pressure, surface area.
  • Higher temperature increases collision energy and frequency.
  • Catalysts lower activation energy.
• Reversible Reactions & Equilibrium:
  • Reactions can revert to original reactants, e.g., Haber Process.
  • Equilibrium is achieved in a closed system when forward and reverse reaction rates are equal.
  • Changing conditions affects equilibrium position (Le Chatelier's Principle).

Organic Chemistry

• Crude Oil & Hydrocarbons:
  • Composed mainly of alkanes (single-bond hydrocarbons).
  • Alkanes separated by fractional distillation.
  • Boiling points vary; longer chains have higher boiling points.
• Alkenes vs. Alkanes:
  • Alkenes have C=C double bonds, are unsaturated.
  • Alkanes are saturated (no C=C bonds).
  • Bromine water test for alkenes: turns colorless.
• Cracking:
  • Converts longer alkanes to shorter ones and alkenes using heat and catalysts.
• Polymers:
  • Addition polymerization of alkenes to form large polymers.
  • Condensation polymerization involves monomers with two functional groups (e.g., alcohols and carboxylic acids).
• Alcohols & Carboxylic Acids:
  • Alcohols react with sodium, oxidized to form carboxylic acids.
  • Functional groups determine properties and reactions.

Chemical Analysis

• Purity Tests:
  • Pure substances have specific melting/boiling points.
• Chromatography:
  • Separates mixtures, calculates RF values to identify substances.
• Gas Tests:
  • Hydrogen: squeaky pop with a burning splint.
  • Oxygen: relights a glowing splint.
  • Carbon Dioxide: turns lime water cloudy.
  • Chlorine: bleaches damp blue litmus paper.
• Flame Tests for Metals:
  • Lithium: crimson, Sodium: yellow, Potassium: lilac, etc.
• Precipitation Reactions:
  • Detect metal ions via reactions with sodium hydroxide.

Atmospheric Chemistry

• Evolution of Atmosphere:
  • Early atmosphere rich in CO2 and nitrogen.
  • Photosynthesis reduced CO2, increased O2.
• Greenhouse Effect:
  • CO2, methane absorb longwave radiation.
  • Increase in gases linked to global warming.
• Pollutants:
  • Carbon monoxide, sulfur dioxide, nitrogen oxides.
  • Cause health issues and environmental damage.

Using Resources

• Sustainability:
  • Meeting demands without compromising future generations.
• Potable Water:
  • Clean water essential; various methods for purification.
• Waste Water Treatment:
  • Involves screening, sedimentation, aerobic treatment.
• Metal Extraction:
  • Traditional methods and newer techniques like phytomining and bioleaching.
• Life Cycle Assessments (LCA):
  • Assess the environmental impact of products.
• Corrosion & Alloys:
  • Rusting and protective methods.
  • Alloys are stronger than pure metals.
• Composites & Polymers:
  • Combining materials for enhanced properties.
• Haber Process:
  • Produces ammonia for fertilizers; involves nitrogen and hydrogen gases.

These notes aim to cover the fundamentals required for the AQA Chemistry Paper 2 exam, providing a condensed study aid for understanding and revising key concepts.