Exam 1 Study Guide: Chapters 1–4

Overview

This study guide covers essential topics from Chapters 1 to 4 in a general chemistry course, focusing on foundational concepts, calculations, and chemical reactions. Emphasis is placed on chemical quantities, stoichiometry, solution chemistry, and reaction types.

Significant Figures and Mathematical Operations

Understanding Significant Figures

• Significant Figures (Sig. Figs): Digits in a measurement that are known with certainty plus one estimated digit.

• Rules:

  • All nonzero digits are significant.

  • Zeros between nonzero digits are significant.

  • Leading zeros are not significant.

  • Trailing zeros are significant only if there is a decimal point.

• Mathematical Operations:

  • Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

  • Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

• Example: (rounded to one decimal place)

Temperature Conversion

Converting Between Temperature Scales

• Celsius to Kelvin:

• Celsius to Fahrenheit:

• Fahrenheit to Celsius:

• Example: Convert to Kelvin:

Density

Definition and Calculation

• Density (d): The mass per unit volume of a substance.

• Formula:

• Units: Commonly g/mL or g/cm3

• Example: If a sample has a mass of 10 g and a volume of 2 mL,

Atomic Structure and Element Symbols

Protons, Neutrons, and Electrons

• Element Symbol: Represents a specific element (e.g., Na for sodium).

• Number of Protons (#p): Equal to the atomic number (Z).

• Number of Electrons (#e): Equal to the number of protons in a neutral atom; for ions, adjust for charge.

• Number of Neutrons (#n):

• Example: For : 11 protons, 12 neutrons, 11 electrons (neutral atom).

Oxidation Numbers

Assigning Oxidation States

• Oxidation Number: The hypothetical charge an atom would have if all bonds were ionic.

• Rules:

  • Elemental form: 0

  • Monatomic ion: Equal to its charge

  • Oxygen: Usually -2

  • Hydrogen: +1 (with nonmetals), -1 (with metals)

  • Sum of oxidation numbers in a compound is 0; in a polyatomic ion, equals the ion's charge.

• Example: In H2O, H = +1, O = -2

Naming Compounds

Systematic Nomenclature

• Ionic Compounds: Name cation first, then anion (e.g., NaCl: sodium chloride).

• Covalent Compounds: Use prefixes (e.g., CO2: carbon dioxide).

• Acids: Binary acids: hydro- + root + -ic acid (e.g., HCl: hydrochloric acid); Oxyacids: root + -ic/-ous acid (e.g., H2SO4: sulfuric acid).

• Example: FeCl3: iron(III) chloride

Mole Concept, Molar Mass, and Number of Molecules

Quantifying Substances

• Mole: Amount of substance containing entities (Avogadro's number).

• Molar Mass: Mass of one mole of a substance (g/mol).

• Number of Molecules:

• Example: 2 moles of H2O contains molecules.

Balancing Chemical Equations

Law of Conservation of Mass

• Balanced Equation: Same number of each atom on both sides of the equation.

• Steps:

  1. Write correct formulas for reactants and products.

  2. Balance elements one at a time using coefficients.

  3. Check that all atoms are balanced.

• Example:

Stoichiometry

Quantitative Relationships in Reactions

• Stoichiometry: Calculation of reactants and products in chemical reactions using mole ratios.

• General Steps:

  1. Convert given quantities to moles.

  2. Use mole ratios from the balanced equation.

  3. Convert moles to desired units (grams, molecules, etc.).

• Example: How many grams of CO2 are produced from 10 g of C in ?

Solubility Rules

Predicting Solubility in Water

• Solubility Rules: Guidelines to predict if an ionic compound dissolves in water.

• Common Rules:

  • All nitrates (NO3-) and alkali metal salts are soluble.

  • Most chlorides, bromides, and iodides are soluble except with Ag+, Pb2+, Hg22+.

  • Most sulfates are soluble except with Ba2+, Pb2+, Ca2+, Sr2+.

  • Most carbonates, phosphates, sulfides, and hydroxides are insoluble except with alkali metals and NH4+.

• Example: NaCl is soluble; AgCl is insoluble.

• Additional info: Solubility rules will not be provided on the exam; memorize key rules.

Molecular, Ionic, and Net Ionic Equations

Representing Reactions in Solution

• Molecular Equation: Shows all reactants and products as compounds.

• Complete Ionic Equation: Shows all strong electrolytes as ions.

• Net Ionic Equation: Shows only species that change during the reaction.

• Example:

  • Molecular:

  • Complete Ionic:

  • Net Ionic:

Redox Reactions

Oxidation-Reduction Processes

• Redox Reaction: Involves transfer of electrons between species.

• Oxidation: Loss of electrons (increase in oxidation number).

• Reduction: Gain of electrons (decrease in oxidation number).

• Half-Reactions: Show oxidation and reduction separately.

• Oxidizing Agent: Causes oxidation; is reduced.

• Reducing Agent: Causes reduction; is oxidized.

• Example:

  • Zn + CuSO4 → ZnSO4 + Cu

  • Oxidation half:

  • Reduction half:

Acid-Base Neutralization

Reactions Between Acids and Bases

• Neutralization: Acid reacts with base to form water and a salt.

• General Equation:

• Example:

Predicting Products of Reactions

Types of Chemical Reactions

• Combination:

• Decomposition:

• Single Displacement:

• Double Displacement:

• Example:

Molarity and Solution Calculations

Concentration and Dilution

• Molarity (M): , where n = moles of solute, V = volume in liters.

• Using Molarity: To find moles:

• Dilution Equation:

• Example: How many moles in 0.5 L of 2 M NaCl? mole

• Example (Dilution): To make 100 mL of 0.5 M solution from 1 M stock: ; L = 50 mL

Precipitation Reactions

Formation of Insoluble Products

• Precipitation Reaction: Two aqueous solutions form an insoluble solid (precipitate).

• Identifying Precipitate: Use solubility rules to determine which product is insoluble.

• Example: (AgCl is the precipitate)

Summary Table: Key Equations and Concepts

Additional info: Questions will focus heavily on Chapters 3 and 4. Solubility rules must be memorized as they will not be provided during the exam.