Chapter 4 (4.1-4.5) Reactions in aqueous solution Electrolytes vs. nonelectrolytes Molecular & ionic equations Precipitation reactions (solubility) Acid/base reactions Oxidation/reduction reactions Concentration of solutions

A solution is a homogenous mixture of 2 or more substances The solute is(are) the substance(s) present in the smaller amount(s) The solvent is the substance present in the larger amount Solution Solvent Solute Soft drink (l) H2O Sugar, CO2 Air (g) N2 O2, Ar, CH4 Soft Solder (s) Pb Sn

An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity. A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity. nonelectrolyte weak electrolyte strong electrolyte

Cations (+) and Anions (-) conduct electricity in solution Strong Electrolyte – 100% dissociation NaCl (s) Na+ (aq) + Cl- (aq) H2O Weak Electrolyte – not completely dissociated CH3COOH CH3COO- (aq) + H+ (aq)

Ionization of acetic acid CH3COOH CH3COO- (aq) + H+ (aq) A reversible reaction. The reaction can occur in both directions. Acetic acid is a weak electrolyte because its ionization in water is incomplete.

Nonelectrolytes do not conduct electricity No cations (+) and anions (-) in solution C6H12O6 (s) C6H12O6 (aq) H2O

So how do you know if it is a strong, weak, or non-electrolyte? Molecular compounds are non. Ionic compounds are strong or weak. ALL insoluble cpds are weak. MOST soluble cpds are strong. Memorize exceptions. Some acids and bases H2O NH3 And more that I won’t ask you to memorize

General solubility rules for salts Soluble All nitrates (NO3-), bicarbonates (HCO3-) and chlorates (ClO3-) All acetates (C2H3O2- or CH3COO-) except Ag+ All halides (Cl-, Br-, I-) except Ag+, Pb2+, Hg22+ All sulfates (SO42-) except Ag+, Ca2+, Sr2+, Ba2+, Pb2+, Hg22+ All alkali metal ion (Na+, K+, Rb+, Li+, Cs+), NH4+ salts All common inorganic acids Insoluble All hydroxides (OH-) except alkali metal ions, NH4+, Ba2+ All chromates (CrO4-), carbonates (CO32-), phosphates (PO43-), and oxalates (C2O42-) except alkali metals and NH4+ All sulfides (S2-) except Na+, K+, NH4+, Mg2+, Ca2+, Ba2+

Some common strong electrolytes Acids HCl HNO3 H2SO4 HClO4 Bases NaOH KOH Ba(OH)2 Etc Salts all soluble salts with a few exceptions, see below. Some common weak electrolytes HC2H3O2 HF HNO2 H3PO4 H2C2O4 H2SO3 H2CO3 H2S NH3 Mg(OH)2 Ca(OH)2 Fe(OH)3 etc Salts/other HgCl2 Pb(C2H3O2)2 H2O

Three types of reactions in aqueous solution (in this chapter) Precipitation reactions Acid/base reactions Oxidation/reduction reactions

Precipitation Reactions Precipitate – insoluble solid that separates from solution precipitate Pb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq) molecular equation Pb2+ + 2NO3- + 2Na+ + 2I- PbI2 (s) + 2Na+ + 2NO3- ionic equation Pb2+ + 2I- PbI2 (s) net ionic equation Na+ and NO3- are spectator ions

Writing Net Ionic Equations Write the balanced molecular equation. Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions. Do NOT dissociate weak electrolytes. Cancel the spectator ions on both sides of the ionic equation AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq) Ag+ + NO3- + Na+ + Cl- AgCl (s) + Na+ + NO3- Ag+ + Cl- AgCl (s)

Three types of reactions in aqueous solution (in this chapter) Precipitation reactions Acid/base reactions Oxidation/reduction reactions

Arrhenius acid is a substance that produces H+ (H3O+) in water Hydronium ion Arrhenius base is a substance that produces OH- in water

A Brønsted acid must contain at least one ionizable proton! A Brønsted acid is a proton donor A Brønsted base is a proton acceptor base acid acid base A Brønsted acid must contain at least one ionizable proton!

CH3COO- (aq) + H+ (aq) CH3COOH (aq) Brønsted base Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4- HI (aq) H+ (aq) + I- (aq) Brønsted acid CH3COO- (aq) + H+ (aq) CH3COOH (aq) Brønsted base H2PO4- (aq) H+ (aq) + HPO42- (aq) Brønsted acid H2PO4- (aq) + H+ (aq) H3PO4 (aq) Brønsted base

Monoprotic acids Diprotic acids Triprotic acids HCl H+ + Cl- Strong electrolyte, strong acid HNO3 H+ + NO3- Strong electrolyte, strong acid CH3COOH H+ + CH3COO- Weak electrolyte, weak acid Diprotic acids H2SO4 H+ + HSO4- Strong electrolyte, strong acid HSO4- H+ + SO42- Weak electrolyte, weak acid Triprotic acids H3PO4 H+ + H2PO4- Weak electrolyte, weak acid H2PO4- H+ + HPO42- Weak electrolyte, weak acid HPO42- H+ + PO43- Weak electrolyte, weak acid