CHEM 101 1st Edition Lecture 8 Outline of Last Lecture I. Introduction to Chemical Reactions and EquationsII. Introduction to the Chemical EquilibriumIII. Aqueous SolutionsIV. Test ReviewOutline of Current Lecture I. Aqueous Solutions continuedII. Solubility of Ionic CompoundsIII. Acids and BasesCurrent LectureChapter 3: Chemical Reactions- Aqueous Solutiono When ions are present in water, the solutions conduct electricityo Ions in solution are called electrolytes. Strong electrolytes are HCl (aq), CuCl2 (aq) and NaCl (aq). - They show a strong tendency to dissociate and to conduct electricity well Acetic acid ionizes only to a small extent; it’s a weak electrolyte.- Weak electrolytes exist in solution under equilibrium conditions- The small concentration of ions conducts electricity poorly.- The molecular (non-dissociated) form is preferred in solution Non-electrolytes- compounds dissolve in water but don’t conduct electricity (Sugar, Ethanol, ethylene glycol)- Do not dissociate (or they show dissociation to a negligible extend) into ions- Solubility of Ionic Compounds in Watero Soluble ionic compounds include: Salts of Na^(+), K^(+), NH4^(+) Salts of NO3^(-), ClO3^(-), ClO4^(-) Salts of Halides, X^(-) Salts of SO4^(2-)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Exceptions include: Halides of Ag^(+), Hg2^(2+), Pb^(2+), MgF2, CaF2, SrF2, BaF2, PbF2, Earth Alkalines: CaSO4, SrSO4, BaSO4, PbSO4, Ag2SO4 MEMORIZE THESE!o Insoluble ionic compounds: Salts of CO3^(2-), PO4^(3-), (COO)2^(2-) (oxalate), CrO4^(2-) (chromate), S^(2-), O^(2-), OH^(-)o Exceptions: Salts of NH4^(+) and alkali metal ions Alkali metal hydroxides Ba(OH)2, Sr(OH)2- Example:o Oxalate o Acetateo Chromate CRO4^(2-)o Sulfate SO4^(2-)- Clicker Questiono Which of the following salts is insoluble in water?A. NH3NO3B. NaOHC. PbI2 (correct)D. K2CO3E. LiCl- Experiment: When equal amounts of aqueous solutions of 0.1 M calcium acetate and 0.1M potassium carbonate are mixed together, a precipitate forms. (1 M= 1 mol/L; unit of concentration of a solution)o When they were added together, they did not mix, but instead formed precipitate which looked like clouds. There was a higher concentration at the top and a lower concentration at the bottom, meaning we had to add more of the potassium carbonate to “mix” it more and make it more even.o Ca(Ac)2(aq) + K2CO3(aq) 2K(Ac)(aq) + CaCO3 (s) The downward arrow is common to represent the precipitate in the formulao Complete Ionic Reaction: Ca^(2+)(aq) + 2Ac^(-)(aq) + 2 K^(+)(aq) + CO3^(2-) (aq) 2K^(+)(aq) + 2Ac^(-)(aq)+ CaCO3 (s) o Net Ionic Equation:Ca^(2+)(aq) + CO3^(2-)(aq) CaCO3 (s)- Clicker Questiono Which is the net ionic equation for the reaction of AgNO3(aq) and Na2Co3(aq)?A. Ag^(+)(aq) +CO3^(2-)(aq) AgCO3(s)B. Na^(+)(aq) +NO3^(2-)(aq) NaNo3(s)C. 2AgNO3(aq) + Na2CO3(aq) 2 NaNO3(aq) +Ag2CO3(s)D. 2Ag^(+)(aq) +CO3^(2-)(aq) Ag2CO3(s) (correct)- Acids and Baseso The Arrhenius Definition: An acid is any substance that increases the H^(+)(aq) concentration in an aqueous solutionHX(aq) H^(+)(aq) + X^(-)(aq) A base is any substance that increases the OH^(-)(aq) concentration in an aqueous solution. MOH(aq)M^(+)(aq) +OH^(-)(aq)o Brønsted-Lowry: An acid is any substance that donates H^(+) to another species in an aqueous solution.HX(aq) + H2O(l) H3O^(+)(aq) + X^(-)(aq) A base is any substance that accepts H^(+) in an aqueous solutionH3O^(+)(aq) + NH3(aq) NH4^(+)(aq) Ex: H2O(l) + NH3(aq) OH^(-)(aq) + NH4(aq)o Strong Acids= strong electrolytes:HNO3(aq) +H2O(l) H3O^(+)(aq) + NO3^(-)(aq)o Strong bases = strong electrolytes:KOH(s) K^(+)(aq) + OH^(-)(aq)o Weak acids = weak electrolytes:HAc(aq) +H2O > Ac^(-) + H3O^(+)(aq)o Weak bases = weak electrolytes:NH3(aq) + H2O(l) NH4^(+)(aq) +OH^(-)(aq)o Example for a polyprotic acid, sulfuric acid: First dissociation step: (Strong Acid)H2SO4(aq) + H2O(l) H3O^(+)(aq) +HSO4^(-)(aq) Second dissociation step: (Weak Acid)HSO4^(=)(aq) + H2O(l) H3O^(+)(aq) + SO4^(2-)(aq) Example:- H3PO4 Phosphoric Acid- Step 1: dissociation of phosphoric acid in waterH3PO4 (aq) + H2O(l) ->H2PO4^(-)(aq) + H3O^(+)(aq)- Step 2: Dissociation of dihydrogen phosphate in waterH2PO4(aq) + H2O(l) -> HPO4^(2-)(aq) + H3O^(+)(aq)- Step 3: Dissociation of the hydrogen phosphate in waterHPO4^(2-) + H2O -> PO4^(3-)(aq) + H3O^(+)(aq) Amphiprotic Compound- a compound that is able to function as a base and an acid. H2PO4(aq) is a base in the products of step 1 and an acid in the reactants of step 2o Reaction between strong acids and strong bases: Neutralization Overall reaction:HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) Complete Ionic Equation:H3O^(+)(aq) + Cl^(-)(aq) + Na^(+)(aq) + OH^(-)(aq) 2 H2O(l) + Na^(+)(aq)+ Cl^(-) Net Ionic Equation:H3O^(+)(aq) + OH^(-)(aq) 2H2O(l)o Reaction between weak acids and strong bases: Overall Reaction:HAc(aq) + NaOH(aq) H2O(l) + NaAc(aq) Complete Ionic Equation:HAc(aq) + Na^(+)(aq) + OH^(-)(aq)H2O(l) + Na^(+)(aq) Ac^(-)(aq) Net Ionic EquationHAc(aq) + OH^(-)(aq)H2O(l) + Ac^(-)(aq)o Reaction between weak acids and strong bases: Net Ionic Equation:HAc(aq) + OH(aq) H2O(l) + Ac^(-)(aq) The Resulting Solution is Basic:Ac^(-)(aq) + H2O(l) HAc(aq) + OH^(-)(aq)(reverse/competing reaction of the equilibriumo Reaction between strong acids and weak bases: Overall Reaction:HCl(aq) + NH3(aq) NH4Cl(aq) Complete Ionic Equation:H3O^(+)(aq) + Cl^(-)(aq) + NH3 (aq) H2O(l) + NH4^(+)(aq) + Cl^(-)(aq) Net Ionic Equation:H3O^(+)(aq) + NH3(aq) H2O(l) + NH4^(+)(aq) The Resulting Solution is Acidic:NH4^(+)(aq) + H2O(l) NH3 (aq) +H3O^(+)(aq)(reverse/competing reaction of the equilibrium)o Oxides of nonmetals such as CO2, SO2, SO3, and NO2 are called acidic oxides since they react to acids with waterCO2(g) +H2O(l) H2CO3(aq)SO2(g) + H2O(l) HSO3(aq)SO3(g) + H2O(l) HSO4(aq)2NO2(g) + H2O(l) HNO3(aq) +
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