Chapter 4 Aqueous Solutions and Solution Stoichiometry

Chapter 4 Aqueous Solutions and Solution Stoichiometry -...

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Unformatted text preview: Aqueous Reactions and Solution Stoichiometry Chapter 4 Aqueous Solutions q Solution - Homogeneous Mixture In an aqueous solution, water is the solvent. Electrolytes q Electrolytes dissolve in water to form ions. q Electrolytes are: qSoluble ionic compounds such as NaCl and AgNO3 qAcids such as HCl and HNO3 qBases such as NaOH Electrolytes allow the flow of electricity through water Dissolving NaCl in Water Dissolve Dissolving Electrolytes q NaCl(s) Na+(aq) + Cl-(aq) q Mg(NO3)2(s) Mg2+(aq) + 2NO3-(aq) q (NH4)3PO4(s) q HCl(g) Nonelectrolytes q What kinds of compounds are nonelectrolytes? Dissolving Nonelectrolytes q CH3OH(l) CH3OH(aq) Strong Electrolytes q Strong electrolytes ionize completely in water. qSoluble ionic compounds (T4.1 and Lab manual) qStrong Acids and Bases (T4.2) qHCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4 NaOH, qNaOH, Ba(OH)2, ... Weak Electrolytes q What is a weak electrolyte? q What types are compounds are weak electrolytes? 1 Which of these compounds is a weak electrolyte? 33% 33% 33% 1. AX 2. AY 3. AZ 1 2 3 1 Aqueous Reactions q Double-Displacement Reactions qalso called Exchange or Metathesis q Single-Displacement Reactions qa type of oxidation-reduction reaction 1 Double-Displacement Reactions (Exchange) AB + CD AD + CB q Examples: q NaCl(aq) + AgNO3(aq) NaNO3(aq) + AgCl(s) q HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) 1 Double-Displacement Reactions (Exchange) AB + CD AD + CB 3 Different types: 1. Precipitation Reaction (a solid forms) 2. Gas-Forming Reaction 3. Acid-Base Neutralization Reactions 1 Mixing Two Aqueous Solutions NaCl(aq) AgNO3(aq) 1 Precipitation Reactions Macroscopic AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) 1 Precipitation Reactions q AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) Complete Ionic Equation: Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) AgCl(s) + Na+(aq) + NO3-(aq) What is the Net Ionic Equation? 1 Net Ionic Equation (Leave out spectators) Ag+(aq) + Cl-(aq) AgCl(s) 1 Solubility Rules 1 Solubility Rules q Know that compounds containing the following ions are water soluble: q Na+ q K+ q NH4+ q NO3q CH3COO- (acetate) 2 What are the products (including phases) of this reaction? 25% 25% Pb(NO3)2(aq) + NaI(aq) ? 1. NaNO3 (s), PbI2 (s) 2. NaNO3 (aq), PbI (s) 3. NaNO3 (aq), PbI (aq) 4. NaNO3 (aq), PbI2 (s) 1 2 25% 25% 3 4 2 Precipitation Reactions AB + CD AD + CB(s) q Predict the products of the reaction, write phases, and then balance the equation: Pb(NO3)2(aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq) 2 Group Work AB + CD AD + CB(s) q Given that a precipitate forms in this reaction, predict the products and their phases, and balance the equation. BaCl2(aq) + Na2CrO4(aq) ? 2 Group Work AB + CD AD + CB(s) q Given that a precipitate forms in this reaction, predict the products and balance the equation. Pb(NO3)2(aq) + K2S(aq) ? 2 What are the spectator ions in this reaction? KNO3(aq) + NaCl(aq) ?? 1. NO3-, Na+ 2. 3. 4. 5. K+, Cl K+, Na Na+, Cl K+, NO3-, Na+, Cl 1 2 3 4 5 20% 20% 20% 20% 20% 2 Gas-forming Reactions AB + CD AD + CB 2. Gas-Forming Reaction Na2CO3(aq) + 2HCl(aq) 2 Gas-forming Reactions AB + CD AD + CB 2. Gas-Forming Reaction Na2CO3(aq) + 2HCl(aq) H2CO3(aq) + 2NaCl(aq) 2 Gas-forming Reactions AB + CD AD + CB 2. Gas-Forming Reaction Na2CO3(aq) + 2HCl(aq) H2CO3(aq) + 2NaCl(aq) H2CO3(aq) CO2(g) + H2O(l) Overall Reaction: Na2CO3(aq) + 2HCl(aq) CO2(g) + H2O(l)+2NaCl(aq) 2 Gas-forming Reactions AB + CD AD + CB 2. Gas-Forming Reaction Predict the products and balance the equation: Na2SO3(aq) + 2HCl(aq) 2 Gas-forming Reactions AB + CD AD + CB 2. Gas-Forming Reaction Predict the products and balance the equation: Na2SO3(aq) +2HCl(aq) SO2(g) + H2O(l)+ 2NaCl(aq) 3 Neutralization Reactions AB + CD AD + CB 3. Neutralization Reactions Acid + Base Salt + water HCl(aq) + Mg(OH)2(s) 3 Neutralization Reactions AB + CD AD + CB 3. Neutralization Reactions q Acid + Base Salt + water 2HCl(aq) + Mg(OH)2(s) MgCl2(aq) + 2H2O(l) 3 What are the spectator ions in this reaction? H3PO4(aq) + NaOH(aq) 1. H+, OH2. Na+, H+ 3. PO43-, OH4. Na+, PO431 2 3 4 25% 25% 25% 25% 3 Oxidation-Reduction Reactions q "Charge" on atom changes from reactants to products. q Electrons are exchanged Example: 2Na + Cl2 2NaCl 2Na 2Na+ + 2e- (Oxidation) Cl2 + 2e- 2Cl- (Reduction) 3 Oxidation-Reduction Reactions q Oxidation: Loss of electrons q Reduction: Gain of electrons 3 Oxidation Numbers q 1. q 2. q 3. Atoms/molecules in elemental form: 0 Monatomic Ions in ionic compounds: ion charge Atoms in Molecular Compounds: -2 except in peroxide O22+1 (when bonded to nonmetals) -1 always -1 except when bonded to Oxygen q Oxygen q Hydrogen q Fluorine q Halogens q 4. The oxidation numbers sum to zero for a compd. 3 Oxidation Numbers q Determine the oxidation number for each element in each substance. H2O2 q TiCl4 q CaH2 q CCl4 q N2O4 q MnO4H2O O2 3 Oxidation Numbers q Determine the oxidation number for each element in each substance. H2O2 +1, -1 q TiCl4 +4, -1 q CaH2 q CCl4 q N2O4 +2, -1 +4, -1 +4, -2 H2O O2 +1, -2 0 q MnO4- +7, -2 3 H2S S8 SO3 SO32- What are the oxidation numbers on sulfur in these compounds? 25% 25% 25% 25% 1. 2. 3. 4. -2,0,-2, -4 +2, 0, -2, +4 -2, 0, +6, +4 -2, +2, +6, +8 1 2 3 4 3 Oxidation Reactions (Redox Reactions) q Which of the following reactions are oxidationreduction reactions? 2Mg(s) + O2(g) 2MgO(s) CaCO3(s) CaO(s) + CO2(g) AgNO3(aq) + HCl(aq) AgCl(s) + HNO3(aq) 2AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + 2Ag(s) 4 Oxidation Reactions (Redox Reactions) q Which of the following reactions are oxidationreduction reactions? 2Mg(s) + O2(g) 2MgO(s) CaCO3(s) CaO(s) + CO2(g) AgNO3(aq) + HCl(aq) AgCl(s) + HNO3(aq) 2AgNO3(aq) + Cu(s) Cu(NO3)2 + 2Ag(s) 4 Single-Displacement Reactions A + BC AC + B q Examples: q Zn(s) + Cu(NO3)2(aq) Zn(NO3)2(aq) + Cu(s) q Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) q 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g) q Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(aq) 4 Single-Displacement Reactions A + BC AC + B q Net Ionic Equations q Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) q Mg(s) + 2H+(aq) Mg2+(aq) + H2(g) q 2Na(s) + 2H2O(l) 2Na+(aq) + 2OH-(aq) + H2(g) q Cl2(g) + 2Br-(aq) 2Cl- (aq) + Br2(aq) 4 Predicting Single-Displacement Reactions A + BC AC + B q Which reaction will occur? Zn(s) +Cu(NO3)2(aq) Zn(NO3)2(aq) + Cu(s) or Cu(s) +Zn(NO3)2(aq) Cu(NO3)2(aq) + Zn(s) q It depends on the relative activities of the metals. See Activity Series T 4.5 4 Which is more Reactive? Zn or Cu? 4 Copper metal plates on Zinc (Zinc transfers electrons to copper!) 4 Describe the electron transfer 4 Single-Displacement Reactions A + BC AC + B q Which reaction will occur? Zn(s) +Cu(NO3)2(aq) Zn(NO3)2(aq) + Cu(s) or Cu(s) +Zn(NO3)2(aq) Cu(NO3)2(aq) + Zn(s) q Zinc metal is more active than copper so zinc metal will lose electrons to form Zn2+. 4 Which is more Active, Zn or Mg? 4 Which is more active, Ag or Cu? Rxn 5 Place Cu, Zn, Mg and Ag in order from most active to least active. q Mg > Zn q Zn > Cu q Cu > Ag q Mg, Zn, Cu, Ag Most..........Least 5 5 Activity Series q Which of the following metals will react with HCl(aq) to form H2 gas? q Silver q Iron 5 Concentrations of Solutions q The concentration of a solution describes the relative amount of solute dissolved in the solvent. q Chemistry often expresses solution concentrations in terms of molarity (M). 5 Molarity = Moles/Liter 5 Molarity q What volume of a 0.40 M NaOH solution contains 0.040 mol of NaOH? 5 Molarity q What volume of a 0.40 M NaOH solution contains 0.040 mol of NaOH? L = ( 0.040mol ) 0.10 L (100 mL) 0.40 mol 5 Molarity q How many moles of HCl are contained in 250 mL of a 0.10 M HCl solution? 5 Molarity q How many moles of HCl are contained in 250 mL of a 0.10 M HCl solution? 0.10 mol = ( 0.250 L ) 0.025mol L 5 What is the molarity of a solution that contains 36.5 grams of HCl dissolved in 250.0 mL of solution? 25% 25% 25% 25% 1. 2. 3. 4. 1.00M 2.00M 4.00M 8.00M 1 2 3 4 6 Molarity of Ions q What is the molarity of ions in each solution? q 2.0 M NaCl q 2.0 M Na2SO4 q 0.15 M Mg3(PO4)2 6 Molarity of Ions q What is the molarity of ions in each solution? q 2.0 M NaCl q 2.0 M Na2SO4 q 0.15 M Mg3(PO4)2 4.0 M ions 6.0 M ions 0.75 M ions 6 Dilutions q Moles of Solute before dilution = moles of solute after dilution molesi = molesf MiVi = MfVf 6 Dilution q What is the concentration of a solution prepared by diluting 2.0 mL of a 6.0 M HCl solution to a total volume of 100.0 mL? 6 Stoichiometry Involving Solutions q In reactions involving solutions, the reagents are available in concentration amounts, usually in molarity units. q Instead of converting from: grams to moles to moles to grams q we convert from: volume to moles to moles to volume 6 MOLARITY GRAMS MOLES VOLUME STOICHIOMETRY using mole ratios 6 Stoichiometry Involving Solutions q What volume of 0.20 M NaOH is required to react with 1.00 L of 0.20 M H2SO4? H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) 6 Stoichiometry Involving Solutions q What is the molarity of a H2SO4 solution if 46.35 mL of 0.1850 M NaOH is required to neutralize 20.00 mL of H2SO4? H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) How would you approach this problem? 6 Stoichiometry Involving Solutions q What is the molarity of a H2SO4 solution if 46.35 mL of 0.1850 M NaOH is required to neutralize 20.00 mL of H2SO4? H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) Molarity of H2SO4= 0.2144 M 6 What is the molarity of a HCl solution if 22.50 mL of 0.1000 M Ca(OH)2 is required to neutralize 20.00 mL of HCl? 2HCl(aq) + Ca(OH)2(aq) CaCl2(aq) + 2H2O(l) 1. 2. 3. 4. 4.5 x 10-3M 0.225M 2.25M 0.450M 25% 25% 25% 25% 1 2 3 4 7 Stoichiometry Involving Solutions Precipitation Reaction: q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 are mixed with 20.0 mL of 0.10 M KI? 7 Stoichiometry Involving Solutions q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 is mixed with 20.0 mL of 0.10 M KI? q First Write a balanced equation: q Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) 7 MOLARITY GRAMS MOLES VOLUME STOICHIOMETRY using mole ratios 7 Stoichiometry Involving Solutions q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 is mixed with 20.0 mL of 0.10 M KI? q Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) q 20.0 mL q 0.10 M q 0.002 mol 20.0 mL 0.10 M 0.002 mol 7 Stoichiometry Involving Solutions q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 is mixed with 20.0 mL of 0.10 M KI? q Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) q 20.0 mL q 0.10 M q 0.002 mol 20.0 mL 0.10 M 0.002 mol limiting reactant 7 Stoichiometry Involving Solutions q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 is mixed with 20.0 mL of 0.10 M KI? q Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) q What reacts: 0.001 mol 0.002 mol q What is produced: 0.001 mol 0.002 mol 7 Stoichiometry Involving Solutions q What mass of PbI2(s) can be produced when 20.0 mL of 0.10 M Pb(NO3)2 are mixed with 20.0 mL of 0.10 M KI? Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) Convert to grams: Mass PbI2 = (0.0010 mol PbI2)(461.0 g/mol) = 0.46 g 7 q Practice Solving Stoichiometry Problems pp. 150-154 7 ...
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