Leaving Cert Chemistry Summary

1. Periodic Table & Atomic Structure

• Subatomic Particles
  • Proton: Charge +1
  • Neutron: Charge 0
  • Electron: Charge -1
  • Relative Masses of subatomic particles
• Isotopes
  • Atoms with same element, different number of neutrons
• Mass Spectrometry
  • Stages: Ionisation, Acceleration, Separation, Detection
• Electron Arrangement
  • Orbitals: s, p, d, f
  • Aufbau Principle
  • Hund's Rule
  • Pauli Exclusion Principle
• Periodic Trends
  • Atomic Radius: Decreases across, increases down
  • Ionisation Energy
  • Electronegativity

2. Bonding

• Ionic Bonds
  • Between metal and non-metal
  • Electron transfer, lattice structure
• Covalent Bonds
  • Sharing electrons
  • Polar vs Non-polar
  • Molecule shapes (VSEPR Theory)
• Intermolecular Forces
  • Van der Waals
  • Dipole-dipole
  • Hydrogen bonding
• Properties
  • Boiling Points
  • Solubility
  • Conductivity

3. Stoichiometry, Formulas & Equations

• Mole Concept
  • 1 mole = 6.022 x 10^23 particles
• Empirical & Molecular Formula
  • Derived from percentage composition
• Balanced Equations
  • Conservation of mass
  • Mole ratio
• Gas Laws
  • Boyle's Law (P1V1 = P2V2)
  • Charles's Law (V1/T1 = V2/T2)
  • Ideal Gas Equation (PV=nRT)

4. Volumetric Analysis

• Titrations
  • Acid-base
  • Redox (e.g., using KMnO4, Na2S2O3)
• Primary Standards
  • Pure, stable, known formula mass
• Indicators
  • Methyl orange
  • Phenolphthalein
  • Starch (for iodine)
• Calculations
  • Molarity
  • Volume
  • Concentration

5. Thermochemistry

• Enthalpy Change (ΔH)
  • Exothermic (ΔH < 0)
  • Endothermic (ΔH > 0)
• Hess's Law
  • Total ΔH = Sum of steps
• Bond Energies
  • ΔH = Bonds broken - Bonds formed
• Heat of Reaction/Neutralisation/Combustion
  • q = mcΔT

6. Rates of Reaction

• Factors Affecting Rates
  • Concentration
  • Temperature
  • Surface Area
  • Catalysts
• Collision Theory
  • Activation Energy
  • Effective Collisions
• Catalysts
  • Lower Activation Energy
  • Heterogeneous vs Homogeneous

7. Chemical Equilibrium

• Dynamic Equilibrium
  • Rates of forward and reverse reactions are equal
• Le Chatelier's Principle
  • Changes in conditions shift equilibrium
• Equilibrium Constants (Kc)
  • Affected only by temperature

8. Acids & Bases

• Definitions
  • Arrhenius: Acids produce H+, Bases produce OH-
  • Brønsted-Lowry: Acids are proton donors, Bases are proton acceptors
• Strength
  • Strong vs Weak acids and bases based on extent of dissociation
• pH Scale
  • pH = -log[H+], involves indicators and titration curves
• Neutralisation
  • Acid + Base → Salt + Water

9. Redox Reactions

• Oxidation
  • Loss of electrons, increase in oxidation number
• Reduction
  • Gain of electrons
• Balancing Redox Reactions
  • In acidic or basic solutions
• Electrochemical Cells
  • Anode (Oxidation), Cathode (Reduction)
• Electrolysis
  • Decomposition using electricity

10. Organic Chemistry

• Homologous Series
  • Alkanes, Alkenes, Alkynes, Alcohols, Carboxylic Acids, Esters
• Isomerism
  • Structural and Geometric (cis/trans)
• Functional Groups
  • Naming and identifying
• Reactions
  • Combustion, Substitution, Addition, Polymerisation, Esterification
• Tests
  • Alkene: Bromine water test (decolourisation)
  • Alcohol: Acidified potassium dichromate
  • Carboxylic Acid: Reacts with sodium carbonate
  • Aldehyde: Fehling's or Tollens' test

11. Industrial Chemistry

• Water Treatment
  • Screening, flocculation, filtration, chlorination, fluoridation, pH control
• Hardness of Water
  • Temporary (removable by boiling), Permanent (needs ion exchange)
• Biological Oxygen Demand (BOD)
  • Measure of pollution
• Chromatography
  • Separation technique
• Green Chemistry
  • Minimising waste, energy-efficient processes

Tips for H1 Grade

• Memorise definitions and equations
• Regular practice with past exam questions
• Thorough understanding of titration and organic experiments
• Focus on understanding mechanisms rather than rote memorisation
• Use diagrams for structures, apparatus, and mechanisms