AP Chemistry Exam Cram Session

Introduction

• Speaker: Jeremy Kug
• Context: Final preparation for the AP Chemistry exam.
• Resources: Print the guided notes PDF from the description for following along.
• For comprehensive review: Visit ultimaterreviewpacket.com for additional resources.

Units Covered

• Overview spans Units 1 through 9 of the AP Chemistry course.

Unit 1: Mass Percent and Chemical Compounds

• Mass Percent: Determine the percentage of each element in a compound by mass.
  • Example: Magnesium Chloride (MgCl₂)
    • Calculate atomic masses: Mg = 24.31 amu, Cl = 35.45 amu
    • Determine compound molar mass and calculate mass percent for each element.
• Comparison of Chlorides:
  • Lighter metals (e.g., Be) in chlorides result in a higher percentage of chloride by mass.

Mass Spectrometry

• Isotopes and Abundance: Each peak in a mass spectrum represents an isotope.
• Average Atomic Mass: Calculated using isotope masses and their percentage abundances.

Electron Configurations

• Writing Configurations: Familiarity with periodic table sections aids in configuration writing.
• Ion Configurations:
  • Chloride ion (Cl⁻): Add one electron to neutral Cl configuration.
  • Aluminum ion (Al³⁺): Remove electrons from the outer shell.

Periodic Table Trends

• Atomic Radius:
  • Largest atoms at bottom left of the table.
  • Atoms at bottom have more electron shells.
  • Atoms on the left have fewer protons, larger radius.
• Ionic Radius:
  • Positive ions (cations) are smaller than negative ions (anions).
  • Isoelectronic species: More protons mean smaller radius.
• Ionization Energy:
  • Greatest at top-right of the table.
  • Fewer shells and more protons increase energy required to remove electrons.

Photoelectron Spectroscopy

• Reading Diagrams: Each peak corresponds to a sublevel, and peak height indicates number of electrons.
• Binding Energy: Peaks farther left indicate more protons due to greater binding energy.

Unit 2: Lewis Structures and Bonding

• Lewis Structures: Start with outer atoms and work inward.
• Types of Bonds:
  • Sigma (σ) and Pi (π) bonds: Single bonds are σ, double bonds are σ + π.
• Hybridization: Based on the number of electron domains.

Molecular Geometry

• Shapes and Angles:
  • Bent, trigonal planar, tetrahedral, etc.
  • Bond angles associated with each geometry.

Polarity and Intermolecular Forces

• Polarity: Determined by molecular shape and charge distribution.
• Intermolecular Forces: London dispersion, dipole-dipole, and hydrogen bonding.

Melting Points and Ionic Compounds

• Columb’s Law: Greater charge magnitude or smaller size increases melting points.
• Dissolution in Water: Ion-dipole interactions determine solubility.

Unit 3: Gas Laws and Spectrophotometry

• Ideal Gas Law: PV = nRT, solve for unknowns in gas problems.
• Spectrophotometry: Use Beer-Lambert Law and calibration curves to determine concentrations.

Stoichiometry

• Steps: Convert to moles, use mole ratios, convert to desired units.
• Solution Stoichiometry: Uses molarity and volume in calculations.

Unit 5: Kinetics and Rate Laws

• Reaction Order: Determined by comparing changes in concentration and rate.
• Rate Laws: Written in terms of reactants and their orders.
• Graphical Method: Identify order by which plot is linear.

Thermochemistry

• Specific Heat Calculations: Use Q = mcΔT to find energy changes.
• Heating/Cooling Curves: Phase changes occur at constant temperature.
• Enthalpy of Formation: Use products minus reactants method.

Unit 7: Equilibrium

• Equilibrium Expressions: Products over reactants, omit solids and liquids.
• ICE Tables: Calculate equilibrium concentrations and constants.
• Le Chatelier’s Principle: System shifts to counteract changes in conditions.

Unit 8: Acids and Bases

• pH and pOH Calculations: Use negative log of ion concentrations.
• Strong vs Weak Acids/Bases: Identify by dissociation in water.
• Titration Curves: Determine equivalence points and calculate concentrations.

Unit 9: Thermodynamics and Electrochemistry

• Entropy: Measure of disorder; gases have highest entropy.
• Gibbs Free Energy (ΔG): Negative ΔG indicates thermodynamic favorability.
• Electrochemical Cells:
  • Galvanic vs Electrolytic cells: Galvanic is spontaneous, electrolytic requires energy input.
  • Calculate cell potential from standard reduction potentials.

Conclusion

• Encouragement to Students: Review and apply the concepts learned throughout the year.
• Reminder: Use resources and prepare thoroughly for the AP Chemistry exam.