Chemistry Concepts: Chapters 4, 5, and 7 Overview

Posted on Aug 27, 2024 in Chemistry

Chapter 4: Reactions in Aqueous Solutions

Key Concepts:

  • Electrolytes:
    • Argon (Ar) is not an electrolyte.
    • A strong electrolyte ionizes completely in solution.
    • A weak electrolyte exists predominantly as molecules in solution.
  • Reactions:
    • Aqueous potassium chloride will react with lead nitrate in an exchange (metathesis) reaction.
    • Zinc sulfide (ZnS) is insoluble in water.
    • A neutralization reaction between an acid and a metal hydroxide produces water and a salt.
    • Oxidation cannot occur without reduction.
  • Acids and Bases:
    • Sulfuric Acid is a diprotic acid.
    • Phosphoric acid is a triprotic acid.
    • Hydrofluoric acid (HF) is a weak acid.
    • The seven strong acids are: Hydroiodic (HI), Hydrobromic (HBr), Nitric (HNO3), Hydrochloric Acid (HCl), Sulfuric Acid (H2SO4), Chloric acid (HClO3), and Perchloric Acid (HClO4).
    • Strong bases include alkali metals, strontium, barium, calcium, and ammonium.
    • Brønsted-Lowry definition: Acids are proton (H+) donors, and bases are proton (H+) acceptors.
    • Arrhenius definition: Acids increase H+ concentration in solution, and bases increase OH- concentration in solution.
  • Other Terms:
    • Molarity is expressed as mol solute/L solution.
    • Oxidation is the loss of electrons, and reduction is the gain of electrons.
    • The point in a titration where the indicator changes is called the end point.
    • An acid reacting with a metal hydroxide produces water (H2O).
    • The solvent in an aqueous solution is water.
    • Molecular equations show the complete formulas of reactants and products, while net ionic equations show only the species that participate in the reaction. Spectator ions are present in the solution but do not participate in the reaction.

Chapter 5: Thermochemistry

Key Concepts:

  • First Law of Thermodynamics: Energy lost by the system is gained by the surroundings.
  • Internal energy can be increased by transferring heat from the surroundings to the system and doing work on the system.
  • A baseball possesses potential energy before being thrown.
  • Adding heat to the system always increases its internal energy.
  • An increase in internal energy always results when the system gains heat and has work done on it by the surroundings.
  • Condensation of water vapor is an exothermic process.
  • A negative ΔH corresponds to an exothermic process.
  • Molecules in motion have kinetic energy.
  • Enthalpy change (ΔH) equals heat transferred at constant pressure.
  • Enthalpy is a state function.
  • An endothermic process has a positive ΔH, while an exothermic process has a negative ΔH.
  • Work requires energy.
  • The SI unit for work is the joule.
  • Standard enthalpy of formation is the heat flow when a substance forms from its elements in their standard states at 1 atm.
  • A bomb calorimeter measures internal energy changes.
  • Thermodynamics studies heat flow and energy changes in processes.
  • “Standard conditions” for enthalpy changes typically mean P = 1 atm and T = 298 K.
  • Hess’s Law: The ΔH for a reaction is the sum of the ΔH values for individual steps.
  • Fuel value is the energy released per gram of substance combusted.
  • Specific heat capacity and calculations related to heat transfer and temperature changes are also covered in this chapter.

Chapter 7: The Periodic Table and Periodic Trends

Key Concepts:

  • Henry Moseley developed the concept of atomic number.
  • The modern periodic table arranges elements by increasing atomic number.
  • First ionization energy increases left to right across a period and increases bottom to top within a group.
  • Halogens have the most negative electron affinities.
  • Atomic radius decreases left to right across a period.
  • Electron affinity becomes increasingly negative left to right across a period.
  • Metals can be solid or liquid at room temperature.
  • Most elements are metals.
  • Reactions of alkali metals and alkaline earth metals with water and hydrogen are discussed.
  • Formation of metal hydroxides and salts from reactions of metal oxides with water and acids are explained.
  • Formation of acids and salts from reactions of nonmetal oxides with water and bases are described.
  • Allotropes are different forms of the same element (e.g., white and red phosphorus).
  • Group 8A contains only nonmetals.
  • Hydrofluoric acid (HF) is a weak acid.