Aqueous Solutions

Ionic Reactions General Rules for dissolution (dissociation) of ionic compounds Only 1 cation and 1 anion are formed Monoatomic ions = subscripts become coefficients for the ions Polyatomic ions = only subscripts outside of parentheses become coefficients Charges of all ions must add up to zero (because compounds are neutral

Examples of Ionic Compounds dissolving in water NaBr (s)  Na+(aq) + Br- (aq) Cr(NO3)3 (s)  Cr3+ (aq) + 3 NO3- (aq)

Practice K2S (s)  FeCl3 (s)  MgBr2 (s)  AlCl3 (s)  Na2Cr2O7 (s)  (NH4)2S (s)  K3PO4 (s) 

Answers K2S (s)  2 K+ (aq) + S2- (aq) FeCl3 (s)  Fe3+ (aq) + 3 Cl- (aq) MgBr2 (s)  Mg2+ (aq) + 2 Br- (aq) AlCl3 (s)  Al3+ (aq) + 3 Cl- (aq) Na2Cr2O7 (s)  2 Na+ (aq) + Cr2O72- (aq) (NH4)2S (s)  2 NH4+ (aq) + S2- (aq) K3PO4 (s)  3 K+ (aq) + PO43- (aq)

Will it dissolve in water? Soluble: Alkali metals, NH4+, ClO3-, ClO4-, acetates, NO3-, and strong acids _____________________________________ Strong Acids = HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4 All other acids are weak

Will it dissolve in water? Sometimes Soluble: Cl-, Br-, I- except with Ag+, Hg22+, and Pb2+ Sulfate except with Hg22+, Pb2+, Ca2+, and Ba2+

Will it dissolve Insoluble: CO32-, CrO42-,Cr2O72-, PO43-, P3- except with Alkali Metals and ammonium S2- except with Alkali Metals, Alkaline Earth Metals and ammonium OH- and O2-except with Alkali Metals and ammonium (slightly soluble with Ca2+, Sr2+, and Ba2+)

Will a rxn occur? Chemical Driving Force Formation of water is the strongest driving force Formation of a precipitate (insoluble compound) Formation of a covalent compound. Many of these are organic acids or gases H2CO3 (aq)  CO2 (g) + H2O (l) H2SO3(aq)  SO2 (g) + H2O (l) NH4OH  NH3 (g) + H2O (l) H2S (aq)  H2S (g)

Practice: Formation of water HCl (aq) + NaOH (aq)  CaO (s) + 2 HCl (aq) 

Practice: Predicting Products Solubility Rules Practice Reactions Always Soluble: Alkali metals, NH4+, ClO3-, ClO4-, acetates, NO3-, and strong acids Cl-, Br-, I- except with Ag+, Hg22+, and Pb2+ KCl + Pb(NO3)2 

Practice: Predicting Product Solubility Rules Practice Reaction Always Soluble: Alkali metals, NH4+, ClO3-, ClO4-, acetates, NO3-, and strong acids Sulfate except with Ag+, Hg22+, Pb2+, Ca2+, Sr2+, and Ba2+ Na2SO4 + Ba(NO3)2 

Practice: Formation of a Gas Gases From Aqueous Soln Practice Reaction H2CO3 (aq)  CO2 (g) + H2O (l) H2SO3(aq)  SO2 (g) + H2O (l) NH4OH  NH3 (g) + H2O (l) H2S (aq)  H2S (g) K2SO3 + HNO3 

Practice: Formation of a Gas Gases from Aqueous Soln: Practice Reaction: H2CO3 (aq)  CO2 (g) + H2O (l) H2SO3(aq)  SO2 (g) + H2O (l) NH4OH  NH3 (g) + H2O (l) H2S (aq)  H2S (g) HCl + CaCO3 

Equations Molecular Equation = show chemical formulas HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)

Equations (Complete) Ionic Equation = show ions for strong electrolytes insoluble compounds (precipitates), gases, and covalent compounds are written as molecules H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)  Na+(aq) + Cl-(aq) + H2O (l)

Equations Net Ionic Equation = Only show substances that are not present on both reactant and product sides. Ex: (Complete) Ionic Equation H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)  Na+(aq) + Cl-(aq) + H2O (l) Ex: Net Ionic Equation H+(aq) + OH-(aq)  H2O (l)

Net Ionic Equations Allows chemists to identify active components of the reaction. Ions not included are considered “spectator ions” H+(aq) + OH-(aq)  H2O (l) So Na+ and Cl- are spectator ions

Net Ionic Equations If all ions cancel on reactant and products side, then there is no driving force and therefore no reaction will occur Ex: Will potassium chloride and sodium nitrate react?

Will potassium chloride and sodium nitrate react? Molecular Equation KCl (aq) + NaNO3 (aq)  NaCl (aq) + KNO3 (aq

Will potassium chloride and sodium nitrate react? Molecular Equation KCl (aq) + NaNO3 (aq)  NaCl (aq) + KNO3 (aq) (Complete) Ionic Equation K+(aq) + Cl-(aq) + Na+(aq) + NO3-(aq)  Na+(aq) + Cl-(aq) + K+(aq) + NO3-(aq)

Will A Reaction Occur? Potassium sulfate is mixed with Barium nitrate

Potassium Sulfate with Barium Nitrate K2SO4(aq) + Ba(NO3)2(aq)  BaSO4(s) + 2 KNO3 (aq)

Potassium Sulfate with Barium Nitrate K2SO4(aq) + Ba(NO3)2(aq)  BaSO4(s) + 2 KNO3 (aq) 2K+(aq) + SO42-(aq) + Ba2+(aq) + 2NO3-(aq)  BaSO4(s) + 2K+(aq) + 2NO3-(aq)

Potassium Sulfate with Barium Nitrate 2K+(aq) + SO42-(aq) + Ba2+(aq) + 2NO3-(aq)  BaSO4(s) + 2K+(aq) + 2NO3-(aq) Net Ionic Equation: SO42-(aq) + Ba2+(aq)  BaSO4(s)