AP Chemistry Exam Cram Session

Introduction

• Video by Jeremy Kug for last-minute review before the AP Chemistry exam.
• Print the free guided notes PDF linked in the video description.
• Comprehensive review available at ultimatereviewpacket.com.
• Review covers units 1 through 9.

Unit 1: Mass Percent & Atomic Mass

Mass Percent Calculation

• Mass percent is calculated by dividing the atomic mass of each element by the total molar mass of the compound and multiplying by 100.
• Example: Magnesium chloride (MgCl2)
  • Magnesium: 24.31 amu
  • Chlorine: 35.45 amu (x2 = 70.90 amu)
  • Total molar mass = 95.21 amu
  • Mass percent Mg = 25.53%, Cl = 74.47%

Patterns in Chlorides

• Lighter elements in chloride compounds tend to have higher mass percent of chloride.

Mass Spectrometry

• Graph represents isotopes of an element and their abundance.
• Example: Element with isotopes at 85 amu and 87 amu, average atomic mass ~85.50 amu, likely rubidium.

Electron Configurations

• Important to write electron configurations for elements and ions.
• Example: Chlorine (Cl) and Chloride ion (Cl-).
• Use periodic table to determine configuration order.

Periodic Table Trends

• Atomic Radius: Largest atoms are at the bottom left; size increases with more electron shells and fewer protons.
• Ionic Radius: Cations are smaller, anions larger.
• First Ionization Energy: Highest at the top right; influenced by proximity to nucleus and number of protons.

Unit 2: Lewis Structures & Molecular Geometry

Lewis Structures

• Draw central atom surrounded by atoms and lone pairs.
• Example: Sulfur difluoride (SF2) and carbon dioxide (CO2).

Bond Types

• Sigma Bonds: Single bonds.
• Pi Bonds: Present in double and triple bonds.

Hybridization & Geometry

• Hybridization based on electron domains.
• Geometry affects molecular shape and bond angles.

Polarity & Intermolecular Forces

• Polar molecules have dipole moments due to unbalanced charges.
• Types of forces: London dispersion, dipole-dipole, hydrogen bonding.

Unit 3: Gas Laws & Spectrophotometry

Gas Laws

• Use PV=nRT for calculations involving pressure, volume, temperature, and moles.

Spectrophotometry

• Use Beer-Lambert Law for concentration and absorbance calculations.
• Calibration curves and outliers in experiments.

Unit 4: Stoichiometry

Net Ionic Equations

• Remove spectator ions to focus on the actual chemical change.

Stoichiometry Steps

1. Convert to moles.
2. Use mole ratio from balanced equation.
3. Convert to desired units (e.g., grams).

Unit 5: Kinetics & Rate Laws

Determining Reaction Orders

• Use experimental data to find reaction orders with respect to different reactants.

Rate Law & Rate Constant

• Write rate laws based on reaction order.
• Calculate rate constant with units from experimental data.

Graphical Determination of Order

• Determine reaction order by the shape of concentration vs. time graphs.

Unit 6: Thermochemistry

Calorimetry

• Use Q=mcΔT for heat transfer problems.
• Consider system equilibrium and specific heat capacities.

Heating Curves

• Understand phase changes and temperature behavior as heat is added.

Enthalpy Calculations

• ΔH = Products - Reactants using enthalpy of formation values.

Unit 7: Equilibrium

Equilibrium Constant Expressions

• Write expressions as products over reactants, omitting solids and liquids.

ICE Tables

• Use to calculate equilibrium concentrations and constants.

Le Chatelier’s Principle

• Predict system changes due to concentration, pressure, temperature.

Unit 8: Acids and Bases

pH and pOH

• Calculate using concentration and known equations.

Strong Acids and Bases

• Recognize and calculate pH directly from concentration.

Weak Acids and Bases

• Use equilibrium expressions and ICE tables for pH calculations.

Salt Solutions

• Determine if ionic compound solutions are acidic, basic, or neutral.

Titrations

• Use titration curves to determine concentrations and equivalence points.

Unit 9: Thermodynamics and Electrochemistry

Entropy and Gibbs Free Energy

• Predict spontaneity using ΔG = ΔH - TΔS.
• Consider entropy changes in reactions.

Electrochemistry

• Galvanic cells: Calculate cell potentials and understand electron flow.
• Write balanced equations for cell reactions and determine electrode changes.