AP Chemistry Cram Session Notes

Introduction

• Presented by Jeremy Kug
• Targeted at students preparing for the AP Chemistry exam
• Offers a brief yet intense review session
• Encouragement to download PDF notes and access additional resources

Unit 1: Mass Percent and Basic Concepts

• Mass Percent Calculation

  • Example: Magnesium Chloride (MgCl₂)
  • Atomic Mass: Mg = 24.31 amu, Cl = 35.45 amu (x2 for Cl)
  • Total Molar Mass: 95.21 amu
  • Mass Percent Calculation:
    • %Mg = (24.31 / 95.21) * 100
    • %Cl = (70.90 / 95.21) * 100
  • Repeat for other compounds (e.g., CaCl₂)

• Mass Spectrometry

  • Used to determine isotopic composition and average atomic mass
  • Graphs show isotopic abundance
  • Example with isotopes at 85 amu and 87 amu

• Electron Configurations

  • Writing electron configurations for atoms and ions
  • Example: Cl, Cl⁻, Al, Al³⁺
  • Understand orbital filling and loss or gain of electrons in ions

• Periodicity

  • Trends in atomic radius and ionic radius
  • Factors: number of electron shells, effective nuclear charge
  • Ionization energy trends: influenced by atomic size and nuclear charge

Unit 2: Molecular Structure

• Lewis Electron Dot Diagrams

  • Central atom placement, bond formation
  • Examples: SF₂, CO₂

• Sigma and Pi Bonds

  • Single bonds = sigma; double bonds = sigma + pi
  • Hybridization: relates to electron domain geometry

• Molecular Geometry and Bond Angles

  • VSEPR theory: predicting shapes and angles
  • Examples of molecular shapes: bent, trigonal planar

• Polarity

  • Determining molecular polarity based on structure
  • Intermolecular forces: London dispersion, dipole-dipole, hydrogen bonding

Unit 3: Stoichiometry and Gas Laws

• Gas Laws

  • Ideal gas law: PV = nRT for moles calculation
  • Partial pressures and mole fraction

• Spectrophotometry

  • Beer-Lambert Law for concentration determination
  • Calibration curves and absorbance readings

• Net Ionic Equations

  • Focus on eliminating spectator ions
  • Examples of redox and precipitation reactions

Unit 4: Thermochemistry and Kinetics

• Calorimetry

  • Q=MCΔT: calculation of heat changes
  • Phase changes and heating curves

• Reaction Kinetics

  • Rate laws and method of initial rates
  • Determining reaction order and rate constants

Unit 5: Equilibrium

• Equilibrium Constants

  • Expressions for Kc and Kp
  • Using ICE tables for equilibrium calculations

• Le Chatelier's Principle

  • Predicting shifts in equilibrium
  • Effects of concentration, pressure, and temperature changes

Unit 6: Acids and Bases

• pH and pOH Calculations

  • Relationships between [H₃O⁺], [OH⁻], pH, and pOH
  • Calculating pH for strong acids and bases

• Weak Acids and Bases

  • Equilibrium expressions (Ka, Kb) and percent ionization

• Salts and Their Reactions

  • Determining if a salt solution is acidic, basic, or neutral

• Titration Curves

  • Equivalence points and half-equivalence points
  • Estimating pKa from titration data

Unit 7: Thermodynamics

• Entropy and Gibbs Free Energy
  • Entropy (ΔS): measure of disorder
  • Gibbs Free Energy (ΔG): determining spontaneity
  • Thermodynamic favorability and temperature dependence

Unit 8: Electrochemistry

• Galvanic Cells

  • Concepts of cathode, anode, and cell potential
  • Constructing cell diagrams and calculating standard cell potentials

• Electrolysis

  • Differences between galvanic and electrolytic cells

Conclusion

• Encouragement to review and utilize resources
• Reminder to focus on key concepts and trends
• Wish for success on the AP Chemistry exam