Lesson 2 Notes: Acids, Bases, Electrolytes, and Net Ionic Equations

Strong Acids and Strong Bases

  • Strong acids: listed in transcript (likely intended): ext{HCl}, ext{HBr}, ext{HI}, ext{HClO}3, ext{H}2 ext{SO}4, ext{HNO}3
    • These are strong electrolytes: they dissociate completely in water.
  • Strong bases: Group 1 hydroxides and some Group 2 hydroxides:
    • Group 1 hydroxides (e.g., ext{NaOH}, ext{KOH}) are strong bases.
    • Group 2 hydroxides that are considered strong bases in common teaching: ext{Ca(OH)}2, ext{Sr(OH)}2, ext{Ba(OH)}_2 (note: solubility varies, but when dissolved they provide OH⁻ readily).
  • Ammonia NH₃ is a base, but not a strong base. It does not end with an “-ate” (the note in transcript likely meant to contrast with oxyacids or polyatomic ions). Ammonia is a weak base in water and does not dissociate completely.
  • Why this matters:
    • Strong acids and bases fully dissociate, giving high conductivity in solution and predictable stoichiometry in reactions.
    • Ammonia, as a weak base, partially accepts protons in water and is a weaker electrolyte.

Weak Acids and Bases; Electrolyte Strength

  • Weak acids and bases:
    • Dissociate only partially in water; ionization is incomplete.
    • They are weak electrolytes and conduct electricity only slightly.
  • Nonelectrolytes vs electrolytes:
    • Strong electrolytes: dissolve/ionize completely; good electrical conductors.
    • Weak electrolytes: dissociate partially; moderate conductivity.
    • Nonelectrolytes: do not dissociate into ions (typically do not conduct electricity).

Acids and Naming conventions

  • Acids start with H (in general, especially binary and oxyacids discussed in this transcript).
  • Binary acids (hydro- prefixes):
    • Example: ext{HF}
      ightarrow ext{hydrofluoric acid}
    • Naming pattern uses the hydro- prefix for binary acids without polyatomic anions.
  • Oxyacids (polyatomic acids):
    • Suffixes depend on the base anion (ate vs. ite):
    • Typical examples:
    • ext{H}2 ext{SO}4
      ightarrow ext{sulfuric acid}
    • ext{H}2 ext{SO}3
      ightarrow ext{sulfurous acid}
    • ext{HNO}_3
      ightarrow ext{nitric acid}
    • ext{HNO}_2
      ightarrow ext{nitrous acid}
    • Rule of thumb: anions ending in -ate give acids ending in -ic (e.g.,
      sulfate SO₄²⁻ → sulfuric acid); anions ending in -ite give acids ending in -ous (e.g., sulfite SO₃²⁻ → sulfurous acid).
  • Example in transcript: Hydrobromic acid (HBr) is a binary acid with the hydro- prefix pattern if treated as binary; many common binary halogen acids use traditional names (hydrochloric, hydrobromic, hydroiodic).

Electrolytes and Ionization Concepts

  • Acids and bases as electrolytes:
    • Strong acids and strong bases are strong electrolytes (fully ionize).
    • Weak acids and bases are weak electrolytes (partially ionize).
  • Polyatomic acids (oxyacids) may be strong or weak electrolytes depending on their strength; in this transcript, the focus is on distinguishing strong vs weak electrolytes and naming conventions.
  • Nonelectrolyte vs electrolyte distinction helps explain electrical conductivity and reaction behavior in aqueous solutions.

Spectator Ions and Net Ionic Equations

  • A precipitation reaction is typically a double displacement (metathesis) reaction that forms a solid product (precipitate):
    • General idea: insoluble product forms from mixing two solutions.
  • The solid is called a precipitate.
  • Spectator ions are ions that appear on both sides of a molecular equation and do not participate in the actual precipitation reaction; they are omitted when writing the net ionic equation.
  • Net ionic equation: the equation that shows only the species that actually participate in the reaction (ions that form the precipitate, or other products).
  • Example 1 (precipitation): Ba(NO₃)₂ + KF → BaF₂(s) + 2 KNO₃
    • Full ionic form (where all soluble salts dissociate):
    • ext{Ba}^{2+}(aq) + 2 ext{NO}3^{-}(aq) + ext{K}^+(aq) + ext{F}^-(aq) ightarrow ext{BaF}2(s) + 2 ext{K}^+(aq) + 2 ext{NO}_3^{-}(aq)
    • Net ionic form: ext{Ba}^{2+}(aq) + 2 ext{F}^{-}(aq)
      ightarrow ext{BaF}_2(s)
    • Spectator ions: ext{K}^+ and ext{NO}_3^{-} are omitted.
  • Example 2 (silver chloride precipitation): AgNO₃ + KCl → AgCl(s) + KNO₃
    • Net ionic: ext{Ag}^+(aq) + ext{Cl}^-(aq)
      ightarrow ext{AgCl}(s)
    • Spectator ions: ext{K}^+ and ext{NO}_3^{-} are omitted.
  • Example 3 (lead hydroxide precipitation): NaOH + Pb(NO₃)₂ → Pb(OH)₂(s) + NaNO₃
    • Net ionic: ext{Pb}^{2+}(aq) + 2 ext{OH}^-(aq)
      ightarrow ext{Pb(OH)}_2(s)
  • Practice problems (net ionic focus)
    • Problem: ext{HClO} + ext{RbOH}
      ightarrow ext{RbClO} + ext{H}_2 ext{O}
    • Ionic form: HClO is a weak acid; in water it can be represented as H⁺ and ClO⁻; RbOH supplies Rb⁺ and OH⁻.
    • Net ionic form (removing spectator ions): ext{H}^+(aq) + ext{OH}^-(aq)
      ightarrow ext{H}_2 ext{O}(l)
    • Problem: AgNO₃ + KCl → AgCl(s) + KNO₃
    • Net ionic: ext{Ag}^+(aq) + ext{Cl}^-(aq)
      ightarrow ext{AgCl}(s)
    • Problem: Pb(NO₃)₂ + 2NaOH → Pb(OH)₂(s) + 2NaNO₃
    • Net ionic: ext{Pb}^{2+}(aq) + 2 ext{OH}^-(aq)
      ightarrow ext{Pb(OH)}_2(s)
  • Note on spectator ions in these practice problems: spectator ions are omitted in the net ionic equations; reactions without a solid precipitate would not be written as a net ionic equation in the same way, but here precipitates are present.
  • Caution: In the transcript, some ions and compounds are garbled (e.g., “Spectator lons,” “Hao+ ROHb+cottho,” etc.). The intended concepts above reflect standard net ionic equation practice.

Practice Problem Summary (reformatted for quick study)

  • Precipitation reaction example (net ionic):
    • Full equation: ext{Ba(NO}3)2(aq) + ext{KF}(aq)
      ightarrow ext{BaF}2(s) + 2 ext{KNO}3(aq)
    • Net ionic: ext{Ba}^{2+}(aq) + 2 ext{F}^-(aq)
      ightarrow ext{BaF}_2(s)
  • Silver chloride precipitation:
    • Full equation: ext{AgNO}3(aq) + ext{KCl}(aq) ightarrow ext{AgCl}(s) + ext{KNO}3(aq)
    • Net ionic: ext{Ag}^+(aq) + ext{Cl}^-(aq)
      ightarrow ext{AgCl}(s)
  • Lead hydroxide precipitation:
    • Full equation: ext{Pb(NO}3)2(aq) + 2 ext{NaOH}(aq)
      ightarrow ext{Pb(OH)}2(s) + 2 ext{NaNO}3(aq)
    • Net ionic: ext{Pb}^{2+}(aq) + 2 ext{OH}^-(aq)
      ightarrow ext{Pb(OH)}_2(s)
  • Neutralization example (acid-base):
    • Problem: ext{HClO}(aq) + ext{RbOH}(aq)
      ightarrow ext{RbClO}(aq) + ext{H}_2 ext{O}(l)
    • Net ionic (removing spectator ions): ext{H}^+(aq) + ext{OH}^-(aq)
      ightarrow ext{H}_2 ext{O}(l)

Connections and implications

  • Conceptual links:
    • Distinguishing strong vs weak electrolytes helps predict conductivity and reaction extent.
    • Recognizing spectator ions simplifies reaction equations and highlights the chemical changes that produce precipitates or other products.
    • Understanding acid naming conventions (binary hydro- vs oxyacids with -ic/-ous endings) aids quick identification of acids and their strengths.
  • Practical relevance:
    • Net ionic equations are essential for solving precipitation and acid-base reactions in aqueous solutions, especially in analytical chemistry and environmental contexts.
  • Ethical/philosophical/practical implications:
    • Accurate representation of chemical reactions supports reproducibility and safety in lab work (e.g., avoiding misinterpretation of ionic species and data).

Key formulas and examples (quick reference)

  • Strong acids (examples): ext{HCl}, ext{HBr}, ext{HI}, ext{HClO}3, ext{H}2 ext{SO}4, ext{HNO}3
  • Strong bases (examples): ext{NaOH}, ext{KOH}, ext{Ca(OH)}2, ext{Sr(OH)}2, ext{Ba(OH)}_2
  • Net ionic forms:
    • ext{Ba}^{2+}(aq) + 2 ext{F}^-(aq)
      ightarrow ext{BaF}_2(s)
    • ext{Ag}^+(aq) + ext{Cl}^-(aq)
      ightarrow ext{AgCl}(s)
    • ext{Pb}^{2+}(aq) + 2 ext{OH}^-(aq)
      ightarrow ext{Pb(OH)}_2(s)
  • Neutralization core: ext{H}^+(aq) + ext{OH}^-(aq)
    ightarrow ext{H}_2 ext{O}(l)