GOB Chemistry Final Exam Study Guide: Key Concepts and Principles

Chapter 1: Chemistry Basics – Matter and Measurement

Classification of Matter

Matter is anything that has mass and occupies space. It can be classified as pure substances or mixtures.

• Pure Substances: Elements or compounds made up of only one type of substance or atom. Examples: oxygen gas (O2), water (H2O).

• Mixtures: Combinations of two or more substances. Can be homogeneous (uniform composition, e.g., salt water) or heterogeneous (non-uniform, e.g., chocolate chip cookie).

Physical and Chemical Properties

• Physical Properties: Characteristics observed without changing the substance's identity (e.g., melting point, density).

• Chemical Properties: Characteristics observed when a substance undergoes a chemical change (e.g., flammability).

Physical and Chemical Changes

• Physical Change: Alters the form or appearance but not the chemical identity (e.g., melting ice).

• Chemical Change: Alters the chemical identity, forming new substances (e.g., rusting iron).

Measurement and Significant Figures

• Use significant figures to reflect the precision of measurements.

• Rules:

  • All nonzero digits are significant.

  • Zeros between significant digits are significant.

  • Leading zeros are not significant; trailing zeros are significant only if there is a decimal point.

Density

• Density is the ratio of mass to volume.

$\text{Density} = \frac{\text{mass}}{\text{volume}}$

Example: A brick stamped 14 karat gold has a mass of 110g and a volume of 95 mL. Density = 1.3 g/mL.

Chapter 2: Atoms and Radioactivity

Subatomic Particles

Atoms are composed of protons, neutrons, and electrons.

• Protons: Positive charge, found in nucleus.

• Neutrons: No charge, found in nucleus.

• Electrons: Negative charge, found in electron cloud.

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in an atom; defines the element.

• Mass Number (A): Sum of protons and neutrons in the nucleus.

$\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$

Isotopes

• Atoms of the same element with different numbers of neutrons.

• Isotopes have the same atomic number but different mass numbers.

Nuclear Radiation and Radioactivity

• Unstable nuclei emit radiation (alpha, beta, gamma) to become more stable.

• Alpha Particle (α): Helium nucleus, 2 protons and 2 neutrons.

• Beta Particle (β): High-energy electron emitted from the nucleus.

• Gamma Ray (γ): High-energy electromagnetic radiation.

Half-Life

• The time required for half of a radioactive sample to decay.

$\text{Amount Remaining} = \text{Initial Amount} \times \left(\frac{1}{2}\right)^{\text{number of half-lives}}$

Chapter 3: Compounds – How Elements Combine

Electron Arrangement and Periodic Table

• Electrons are arranged in shells and subshells around the nucleus.

• Valence electrons are in the outermost shell and determine chemical reactivity.

• Groups (columns) indicate the number of valence electrons for main group elements.

• Periods (rows) indicate the number of electron shells.

Ionic and Covalent Bonds

• Ionic Bonds: Transfer of electrons from metals to nonmetals, forming ions.

• Covalent Bonds: Sharing of electrons between nonmetals.

Predicting Ionic Charges

• Main group elements form ions with predictable charges based on their group number.

Writing Formulas and Naming Compounds

• Use the charges of ions to write correct formulas for ionic compounds.

• Name compounds according to IUPAC rules.

Chapter 4: Introduction to Organic Compounds

Organic Compounds and Functional Groups

• Organic compounds contain carbon and hydrogen, often with oxygen, nitrogen, or other elements.

• Alkanes: Saturated hydrocarbons with only single bonds (general formula: CnH2n+2).

• Cycloalkanes: Ring structures (general formula: CnH2n).

• Functional groups are specific groups of atoms that impart characteristic properties (e.g., alcohols, carboxylic acids).

Chapter 5: Chemical Reactions

Types of Chemical Reactions

• Exothermic: Release energy (heat).

• Endothermic: Absorb energy.

• Spontaneous: Occur without external input.

• Nonspontaneous: Require energy input.

Reaction Energy Diagrams

• Show the energy changes during a reaction, including activation energy and enthalpy change.

Factors Affecting Reaction Rates

• Temperature, concentration, catalysts, and surface area can affect how fast reactions occur.

Chapter 7: States of Matter and Their Attractive Forces

Properties of Gases

• Gases have no definite shape or volume and expand to fill their container.

• Gas laws describe the relationships between pressure, volume, temperature, and amount.

Gas Laws: $P_1V_1 = P_2V_2$ (Boyle's Law) $V_1/T_1 = V_2/T_2$ (Charles's Law) $P_1/T_1 = P_2/T_2$ (Gay-Lussac's Law) $PV = nRT$ (Ideal Gas Law, where R = 0.0821 \text{ L·atm·mol}^{-1}\text{K}^{-1})

Intermolecular Forces

• London Dispersion Forces: Weak, present in all molecules.

• Dipole-Dipole Interactions: Between polar molecules.

• Hydrogen Bonding: Strongest, occurs when H is bonded to N, O, or F.

Chapter 8: Solution Chemistry

Solutions and Solubility

• Solute: Substance being dissolved.

• Solvent: Substance doing the dissolving (usually present in greater amount).

• Solubility depends on temperature, pressure, and the nature of solute and solvent.

Concentration Units

• Molarity (M): Moles of solute per liter of solution.

$\text{Molarity} = \frac{\text{moles of solute}}{\text{liters of solution}}$

Electrolytes

• Strong Electrolytes: Completely ionize in solution (e.g., NaCl, HCl).

• Weak Electrolytes: Partially ionize (e.g., acetic acid).

• Nonelectrolytes: Do not ionize (e.g., sugar).

Chapter 9: Acids, Bases, and Buffers in the Body

Acids and Bases

• Acids: Donate protons (H+), turn litmus red.

• Bases: Accept protons, turn litmus blue.

pH Scale

• Measures acidity or basicity of a solution.

$\text{pH} = -\log[\text{H}^+]$

• pH < 7: Acidic; pH = 7: Neutral; pH > 7: Basic.

Acid Strength and Ka

• Ka: Acid dissociation constant; larger Ka means a stronger acid.

Additional Info

• These notes cover the main topics from Chapters 1–9 of a typical GOB Chemistry course, including matter, atomic structure, bonding, reactions, states of matter, solutions, and acid-base chemistry.