General Chemistry Exam 2 Study Guide: Chapters 5, 6, and 8

General Chemistry Exam 2 Study Guide

Overview

This study guide outlines the key topics, concepts, and problem-solving skills required for Exam 2 in a General Chemistry course. The exam will cover material from Chapters 5, 6, and 8, focusing on chemical bonding, molecular structure, and the properties of gases. Students are expected to demonstrate proficiency in both conceptual understanding and quantitative problem-solving using dimensional analysis and conversion factors.

Chapter 4 Review: Essential Skills

Conversion Factors and Dimensional Analysis

• Understand and use unit conversions, density, volume, and other derived units.

• Apply multiple-step calculations using conversion factors.

• Key concepts:

  • Chemical formulas (empirical and molecular)

  • Molar mass (g/mol)

  • Density (mass/volume)

  • Percent composition (mass %)

  • Avogadro's number ($6.022 \times 10^{23}$)

  • Stoichiometry (mole relationships in chemical equations)

• Empirical and Molecular Formulas:

  • Determine a formula from percent composition data.

  • Use molar mass to convert an empirical formula to a molecular formula.

Chapter 5: Chemical Bonding and Molecular Structure

Lewis Structures and Bonding

• Draw Lewis structures for:

  • Binary molecules

  • Molecules with one central atom

  • Simple polyatomic ions

  • Molecules and polyatomic ions with multiple bonds

  • Molecules and polyatomic ions with incomplete or expanded octets

• Recognize when to draw resonance structures and understand their significance.

• Formal charge: Calculate and use to determine the most stable Lewis structure.

VSEPR Theory and Molecular Geometry

• Predict electron group geometry and molecular shape using VSEPR theory.

• Bond angles: Know standard bond angles (e.g., 109.5°, 120°, 180°) and assign them correctly.

• Polarity: Determine if a molecule is polar or non-polar based on shape and electronegativity.

Bonding Theories and Electronegativity

• Classify bonds as ionic, polar covalent, or covalent using periodic trends and electronegativity.

• Use periodic trends to predict bond character.

• Draw and interpret dipole moments and molecular polarity.

Intermolecular Forces

• Identify and compare types of intermolecular forces:

  • Dispersion (London) forces

  • Dipole-dipole forces

  • Hydrogen bonding

• Relate structure to physical properties such as boiling and melting points.

Chapter 6: Chemical Bonding II (Advanced Topics)

Resonance and Formal Charge

• Draw resonance structures and understand their role in molecular stability.

• Assign formal charges and use them to select the most likely Lewis structure.

Bond Order and Bond Energy

• Calculate bond order from Lewis structures and resonance forms.

• Relate bond order to bond strength and length.

Expanded Octets and Exceptions

• Recognize molecules with expanded octets (more than 8 electrons around the central atom).

• Identify exceptions to the octet rule (e.g., odd-electron species, electron-deficient molecules).

Chapter 8: Gases and Their Properties

Physical Properties of Gases

• Describe properties such as low density, compressibility, and ability to fill a container.

• Relate macroscopic properties (pressure, volume, temperature) to molecular behavior.

Gas Laws

• Boyle's Law: $P_1V_1 = P_2V_2$ (at constant T and n)

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant P and n)

• Avogadro's Law: $\frac{V_1}{n_1} = \frac{V_2}{n_2}$ (at constant P and T)

• Ideal Gas Law: $PV = nRT$

• Combined Gas Law: $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$

Gas Mixtures and Partial Pressures

• Dalton's Law of Partial Pressures: $P_{\text{total}} = P_1 + P_2 + \ldots$

• Calculate mole fractions and use them to determine partial pressures.

Density and Molar Mass of Gases

• Relate density to molar mass: $d = \frac{PM}{RT}$

• Determine molar mass from gas density measurements.

Kinetic Molecular Theory

• Explain gas behavior using the kinetic molecular theory.

• Relate temperature to average kinetic energy: $KE_{\text{avg}} = \frac{3}{2}RT$ (per mole)

• Understand diffusion and effusion (Graham's Law): $\frac{\text{rate}_1}{\text{rate}_2} = \sqrt{\frac{M_2}{M_1}}$

Sample Problem Table: Gas Law Calculations

Given	Find	Equation
Initial and final P, V, T	Final P, V, or T	Combined Gas Law: $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$
n, T, V	P	Ideal Gas Law: $PV = nRT$
Partial pressures, mole fractions	Total pressure	Dalton's Law: $P_{\text{total}} = \sum P_i$
Density, P, T	Molar mass	$d = \frac{PM}{RT}$

Problem-Solving Strategies

• Show all work and units in calculations.

• Organize solutions by chapter and topic.

• Use dimensional analysis for multi-step problems.

• Refer to key equations and summary tables in your textbook.

• Practice with suggested textbook problems for each chapter.

Additional Info

• Bring a scientific calculator (no cell phones or smart watches allowed).

• Reference sheets will be provided during the exam.

• Extra paper will be available for problem solving.

• Review lecture notes, textbook chapters, and discussion worksheets.