AP Chemistry Sample Multiple Choice Questions

Introduction

• Recommendation: Check out the website for AP Chemistry resources and sample problems before watching the video.
• Disclaimer: Lecture involves strategies to better understand and solve AP Chemistry test questions.

Stoichiometry without Calculators

• Example Problem: Reaction between iron and sulfur forming iron (II) sulfide.
• Key Concept: Limiting reagent concept and stoichiometry without calculators.
• Calculation Approach:
  • Iron has a higher molar mass and less moles than sulfur for the same mass, thus it's the limiting reagent.
  • Outcome: Reaction vessel contains iron (II) sulfide and excess sulfur.

Bronsted-Lowry Acids and Bases

• Concept: Identification of Bronsted-Lowry acid and its conjugate base.
• Example Answer: [H2PO4- / HPO4 2-] is the correct acid-base pair, differing by one proton.
• Common Mistakes:
  • Not considering strong acids (e.g., nitric acid) which completely dissociate.
  • Misidentifying pairs that do not differ by a single proton.

Photoelectron Spectroscopy (PES)

• Key Points:
  • PES graphs display electron distribution across different energy levels.
  • Y-axis typically represents number of electrons, and X-axis represents energy levels.
• Analysis: Interpretation of PES graph data to identify elements or electron configuration.
• Example Problem: Aluminum, based on electronic configuration and PES graph interpretation.

Solubility and Ion Concentration

• Example on calculating concentration of ammonium phosphate based on its dissociation in water and given molarity of ammonium.

Titration Concept

• Explained with an antacid tablet containing calcium hydroxide titrated with hydrochloric acid.
• Calculation involves determining the mass of calcium hydroxide in the tablet using titration data.

Oxyacids and Ionization

• Discussion on oxyacids and factors influencing their strength and percent ionization.
  • More oxygens around central atom increase acid strength due to electron pulling effect.

Reaction Spontaneity

• Analysis based on enthalpy and entropy contributions to a reaction's spontaneity.

Lab Procedures and Error Prevention

• Focus on proper lab technique to prevent dilution of solutions in titrations.

Kinetics and Rate Laws

• Application of the method of initial rates to determine reaction order with respect to reactants.

Le Chatelier's Principle

• Discussion on how changes in reaction conditions (e.g., temperature, concentration) affects the direction of equilibrium shift.

Dissociation of Ionic Compounds and Strong Acids

• Demonstrated with nitric acid's complete dissociation in water.

Net Ionic Equations

• Explanation of how to write net ionic equations for reactions, distinguishing between reacting species and spectator ions.

Solubility and Common Ion Effect

• Explanation of how the presence of a common ion affects the solubility of a salt in solution.

Molecular Polarity

• Criteria for determining overall molecular polarity despite the presence of polar bonds.

Periodic Trends

• Comparison of lithium and cesium to discuss trends in ionization energy, atomic radius, and electronegativity within a group.

Dalton's Law of Partial Pressures

• Use of Dalton's law to calculate partial pressures of gases in a mixture.

Electron Configurations and Ion Identification

• Strategies for determining the identity of species based on electron configuration.

Specific Heat Capacity Calculations

• Calculation involving the transfer of heat between substances and determination of mass based on specific heat capacity data.

Electrochemistry

• Concepts related to galvanic cells, including calculation of cell potential and changes in electrode mass.