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

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

Overview

This study guide outlines the key topics and skills required for Exam 2 in a General Chemistry course, focusing on Chapters 5, 6, and 8. The exam emphasizes problem-solving using dimensional analysis, conversion factors, and the application of chemical principles related to molecular structure, chemical bonding, and the properties of gases.

Chapter 5: Chemical Calculations and Conversion Factors

Key Concepts

• Units and Conversion Factors: Understanding and using units such as moles, grams, liters, and their derived units in chemical calculations.

• Dimensional Analysis: Applying conversion factors to solve multi-step problems involving chemical quantities.

• Mole Concept: Relating mass, number of particles, and volume to moles using Avogadro's number and molar mass.

Important Formulas

• Mole Calculations: $\text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}$

• Avogadro's Number: $1\ \text{mol} = 6.022 \times 10^{23}\ \text{particles}$

• Percent Composition: $\text{Percent composition} = \frac{\text{mass of element in 1 mol of compound}}{\text{molar mass of compound}} \times 100\%$

Empirical and Molecular Formulas

• Determine empirical formulas from experimental data.

• Calculate molecular formulas using molar mass and empirical formula.

Example

• Given the mass percentages of elements in a compound, determine its empirical and molecular formulas.

Chapter 6: Chemical Bonding and Molecular Structure

Key Concepts

• Lewis Structures: Drawing Lewis structures for binary molecules, polyatomic ions, and molecules with multiple bonds.

• Resonance Structures: Identifying when resonance is appropriate and drawing resonance forms.

• Electronegativity and Bond Polarity: Classifying bonds as ionic, polar covalent, or nonpolar covalent using electronegativity differences.

• Electron Group Geometry: Predicting molecular shapes using VSEPR theory.

Important Formulas and Concepts

• Bond Angles: Common bond angles include 109.5°, 120°, and 180°, depending on electron group geometry.

• Polarity: Determining if a molecule is polar or non-polar based on shape and bond dipoles.

Example

• Draw the Lewis structure for CO2 and determine if the molecule is polar or non-polar.

Chapter 8: Properties of Gases

Key Concepts

• Physical Properties of Gases: Understanding intermolecular forces, low density, and the relationship between pressure, volume, and temperature.

• Kinetic Molecular Theory: Explaining gas behavior at the molecular level.

• Gas Laws: Applying Boyle's Law, Charles's Law, and Avogadro's Law to relate pressure, volume, temperature, and amount of gas.

• Ideal Gas Law: Using the equation $PV = nRT$ to solve problems involving gases.

• Partial Pressures: Dalton's Law of Partial Pressures for mixtures of gases.

• Density and Molar Mass of Gases: Calculating density and molar mass using the ideal gas law.

Important Formulas

• Boyle's Law: $P_1V_1 = P_2V_2$

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$

• Avogadro's Law: $\frac{V_1}{n_1} = \frac{V_2}{n_2}$

• Ideal Gas Law: $PV = nRT$

• Dalton's Law of Partial Pressures: $P_{\text{total}} = P_1 + P_2 + P_3 + \ldots$

Example

• A sample of gas occupies 31.9 mL at 372 K and 1.25 atm. What is the pressure if the volume is expanded to 63.8 mL at a temperature of 398 K?

Suggested Problem-Solving Strategies

• Organize work by chapter and topic.

• Show all steps and units in calculations.

• Use conversion factors and dimensional analysis for multi-step problems.

• Refer to key equations and skills listed in the textbook.

• Practice with suggested textbook problems for each chapter.

Sample Table: Comparison of Gas Laws

Law	Equation	Variables Held Constant	Relationship
Boyle's Law	$P_1V_1 = P_2V_2$	Temperature, amount of gas	Pressure inversely proportional to volume
Charles's Law	$\frac{V_1}{T_1} = \frac{V_2}{T_2}$	Pressure, amount of gas	Volume directly proportional to temperature
Avogadro's Law	$\frac{V_1}{n_1} = \frac{V_2}{n_2}$	Pressure, temperature	Volume directly proportional to amount of gas
Ideal Gas Law	$PV = nRT$	None	Relates all four variables

Additional Info

• Students are encouraged to use reference sheets and calculators during the exam.

• Extra paper will be provided for problem solving.

• Practice problems and textbook exercises are recommended for exam preparation.