Presentation on theme: "TYPES OF CHEMICAL REACTIONS AND SOLUTION STOICHIOMETRY"— Presentation transcript:
1 TYPES OF CHEMICAL REACTIONS AND SOLUTION STOICHIOMETRY Chapter Four:TYPES OF CHEMICAL REACTIONS AND SOLUTION STOICHIOMETRY講義
2 Assignment for Chapter 4 12,20,27,35,47,57,63,75,83,95,107.
3 Core MaterialsChemical reactions in solution are very important in everyday life.Water is a polar solvent that dissolves many ionic and polar substances.ElectrolytesAcids and bases: Arrhenius model, BrØnsted-Lowry model.MolarityTypes of equations that describe solution reactions: Formula equation; Complete ionic equation; Net ionic equation.Solubility rulesImportant types of solution reactions: Acid-base reactions; Precipitation reactions; Oxidation-reduction reactions.Titrations: Stoichiometric(equivalence)point;Endpoint: Oxidation-reduction reactions: Oxidation, Reduction,Oxidizing agent,Reducing agent.
4 Chemical Impact Arrhenius A Man with Solutions (p.132) Science is a human endeavor, subject to frailtiesand governed by personalities, politics, and prejudices.One of the best illustrations of the often bumpy path ofThe advancement of scientific knowledge is the story ofSwedish chemist Svante Arrhenius.……Such a setbakc could have ended his scientific career, butArrhenius was a crusader; he was determined to see histheory thriumph. He promptly embarked on a politicalcampaign, enlisted the aid of several prominent scientists,to get his theory accepted.Ultimately, the ionic theory triumphed. Arrhenius’ fameSpread, and honors heaped on him, culminating in theNobel Prize in chemistry in Not one to rest on hislaurels., Arrhenius turned to new fields, including astronomy,He formulated a new theory that the solar system may haveCome into being through the collision of stars. His exceptionalVersatility led him to study the use of serums to fight disease,Energy resources and conservation, and the origin of life.
5 Nature of Aqueous Solutions Solute – substance being dissolvedSolvent – liquid waterElectrolyte – substance that when dissolved in water produces a solution that can conduct electricity4.2
6 Water, the Common Solvent One of the most important substances on earthCan dissolve many different substancesA polar molecule4.1
7 Water, the Common Solvent, with many uncommon properties One of the most important substances on earthCan dissolve many different substancesA polar moleculeLowest density at 4 oC,Ice is lighter than water,Large specific heat,Large vaporization and melting heats,….4.1
20 ElectrolytesStrong Electrolytes – conduct current very efficiently (bulb shines brightly)Weak Electrolytes – conduct only a small current (bulb glows dimly)Nonelectrolytes – no current flows (bulb remains unlit)4.2
25 Concept CheckWhich of the following solutions contains the greatest number of ions?400.0 mL of 0.10 M NaCl.300.0 mL of 0.10 M CaCl2.200.0 mL of 0.10 M FeCl3.800.0 mL of 0.10 M sucrose.a) contains mol of ions (0.400×0.10×2). b) contains mol of ions (0.300×0.10×3). c) contains mol of ions (0.200×0.10×4). d) does not contain any ions because sucrose does not break up into ions. Therefore, letter b) is correct.4.3
26 Let’s Think About ItDraw molecular level pictures showing each solution. Think about relative numbers of ions.How many moles of each ion are in each solution?4.3
27 NoticeThe solution with the greatest number of ions is not necessarily the one in which:the volume of the solution is the largest.the formula unit has the greatest number of ions.4.3
28 DilutionThe process of adding water to a stock solution to achieve the molarity desired for a particular solution.Dilution with water does not alter the numbers of moles of solute present.Moles of solute before dilution = moles of solute after dilutionM1V1 = M2V24.3
29 Types of Chemical Reactions Precipitation ReactionsAcid-Base ReactionsOxidation-Reduction Reactions4.4
30 Precipitation Reaction A double displacement reaction in which a solid forms and separates from the solution.When ionic compounds dissolve in water, the resulting solution contains the separated ionsPrecipitate – the solid that forms4.5
31 Figure Molecular-Level Representations Illustrating the Reaction of KCl (aq) with AgNO3 (aq) to Form AgCl (s)
32 Precipitation of Silver Chloride KCl (aq) + AgNO3 (aq) AgCl (s) + K+(aq) +NO3 – (aq)Cl– (aq) + Ag+ (aq) AgCl (s)
33 The Reaction of K2CrO4(aq) and Ba(NO3)2(aq) Ba2+(aq) + CrO42–(aq) → BaCrO4(s)solid BaCrO4 formed4.5
34 PrecipitatesSoluble – solid dissolves in solution; (aq) is used in reactionInsoluble – solid does not dissolve in solution; (s) is used in reactionInsoluble and slightly soluble are often used interchangeably4.5
35 Simple Rules for Solubility Most nitrate (NO3) salts are soluble.Most alkali (group 1A) salts and NH4+ are soluble.Most Cl, Br, and I salts are soluble (except Ag+, Pb2+, Hg22+).Most sulfate salts are soluble (except BaSO4, PbSO4, Hg2SO4, CaSO4).Most OH salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble).Most S2, CO32, CrO42, PO43 salts are only slightly soluble.4.5
36 Table 4.1 Simple Rules for the Solubility of Salts in Water
37 Describing Reactions in Solution Formula Equation (Molecular Equation)Reactants and products as compoundsAgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)Complete Ionic EquationAll strong electrolytes shown as ionsAg+(aq) + NO3(aq) + Na+(aq) + Cl(aq) AgCl(s) + Na+(aq) + NO3(aq)4.6
38 Describing Reactions in Solution Net Ionic EquationShow only components that actually reactAg+(aq) + Cl(aq) AgCl(s)Na+ and NO3 are spectator ions4.6
39 Concept CheckYou have two separate beakers with aqueous solutions, one with 4 “units” of potassium sulfate and one with 3 “units” of barium nitrate.Draw molecular level diagrams of both solutions.The first beaker should have 8 K+ ions and 4 SO42- ions. The second beaker should have 3 Ba2+ ions and 6 NO3- ions.4.6/4.7
40 Concept CheckYou have two separate beakers with aqueous solutions, one with 4 “units” of potassium sulfate and one with 3 “units” of barium nitrate.b) Draw a molecular level diagram of the mixture of the two solutions before a reaction has taken place.Now all of the ions should be mixed together in one beaker.4.6/4.7
41 Concept CheckYou have two separate beakers with aqueous solutions, one with 4 “units” of potassium sulfate and one with 3 “units” of barium nitrate.c) Draw a molecular level diagram of the product and solution formed after the reaction has taken place.There should be 8 K+ ions, 6 NO3- ions, 1 SO42- ion, and 3 units of solid BaSO4 formed in the beaker.4.6/4.7
42 Solution Stoichiometry Problems Identify the species present in the combined solution.Write the balanced net ionic equation.Calculate the moles of reactants.Determine limiting reactant.Calculate the moles of product(s).Convert to grams or other units.4.7
51 Key Titration TermsTitrant – solution of known concentration used in titrationAnalyte – substance being analyzedEquivalence point – enough titrant added to react exactly with the analyteEndpoint – the indicator changes color so you can tell the equivalence point has been reached4.8
52 Performing Calculations for Acid-Base Reactions List initial species and predict reaction.Write balanced net ionic reaction.Calculate moles of reactants.Determine limiting reactant.Calculate moles of required reactant or product.Convert to grams or volume, as required.4.8
53 Oxidation-Reduction Reactions (Redox Reactions) Reactions in which one or more electrons are transferred.4.9
56 Rules for Assigning Oxidation States Oxidation state of an atom in an element = 0Oxidation state of monatomic element = chargeOxygen = 2 in covalent compounds (except in peroxides where it = 1)Hydrogen = +1 in covalent compoundsFluorine = 1 in compoundsSum of oxidation states = 0 in compoundsSum of oxidation states = charge of the ion4.9
58 ExerciseFind the oxidation states for each of the elements in each of the following compounds:K2Cr2O7CO32-MnO2PCl5SF4K2Cr2O7; K = +1; Cr = +6; O = -2CO32-; C = +4; O = -2MnO2; Mn = +4; O = -2PCl5; P = +5; Cl = -1SF4; S = +4; F = -14.9
59 Redox Characteristics Transfer of ElectronsTransfer may occur to form ionsOxidation – increase in oxidation state (loss of electrons); reducing agentReduction – decrease in oxidation state (gain of electrons); oxidizing agent4.9
60 Figure 4.20 A Summary of Oxidation-Reduction Process
61 Concept CheckWhich of the following are oxidation-reduction reactions? Identify the oxidizing agent and the reducing agent.a) Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)b) Cr2O72-(aq) + 2OH-(aq) 2CrO42-(aq) + H2O(l)c) 2CuCl(aq) CuCl2(aq) + Cu(s)Zn – reducing agent; HCl – oxidizing agentc) CuCl acts as the reducing and oxidizing agent4.9
62 Balancing Oxidation-Reduction Reactions Cr2O72-(aq) + SO32-(aq) Cr3+(aq) + SO42-(aq)How can we balance this equation?First Steps:Separate into half-reactionsBalance elements except H and O4.10
64 Method of Half Reactions Cr2O72-(aq) 2Cr3+(aq) SO32-(aq) SO42-(aq)How many electrons are involved in each half reaction?4.10
65 Method of Half Reactions (continued) 6e- + Cr2O72-(aq) 2Cr3+(aq) SO32-(aq) + SO42-(aq) + 2e-How can we balance the oxygen atoms?4.10
66 Method of Half Reactions (continued) 6e- + Cr2O72-(aq) Cr3+(aq) + 7H2O H2O +SO32-(aq) + SO42-(aq) + 2e-How can we balance the hydrogen atoms?4.10
67 Method of Half Reactions (continued) This reaction occurs in an acidic solution.14H+ + 6e- + Cr2O72- 2Cr3+ + 7H2O H2O +SO32- SO e- + 2H+How can we balance the electrons?4.10
68 Method of Half Reactions (continued) 14H+ + 6e- + Cr2O72- 2Cr3+ + 7H2O3[H2O +SO32- SO e- + 2H+]Final Balanced Equation:Cr2O SO H+ 2Cr3+ + 3SO H2O4.10
69 ExerciseBalance the following oxidation-reduction reaction that occurs in acidic solution.Br-(aq) + MnO4-(aq) Br2(l)+ Mn2+(aq)10Br-(aq) + 16H+(aq) + 2MnO4-(aq) 5Br2(l)+ 2Mn2+(aq) + 8H2O(l)4.10
70 Half-Reaction Method – Balancing in Base Balance as in acid.Add OH that equals H+ ions (both sides!)Form water by combining H+, OH. Cancel any water molecules that appear on both sides.Check elements and charges for balance.4.10
71 For ReviewChemical reactions in solution are very important in everyday life.Water is a polar solvent that dissolves many ionic and polar substances.Electrolytes˙Strong electrolyte: 100% dissociated to produce separate ions; strongly conducts an electric current˙Weak electrolyte: Only a small percentage of dissolved molecules produce ions; weakly conducts an electric current˙Nonelectrolyte: Dissolved substance produces no ions; does not conduct an electric currentAcids and bases˙Arrhenius model: Acid: produces H+; Base: produces OH-˙BrØnsted-Lowry model: Acid: proton donor; Base: proton acceptor˙Strong acid: completely dissociates into separated H+ and anions˙Weak acid: dissociates to a slight extentMolarity˙One way to describe solution composition˙Moles of solute after dilution=moles of solute before dilutionTypes of equations that describe solution reactions˙Formula equation: all reactants and products are written as complete formulas˙Complete ionic equation: all reactants and products that are strong electrolytes are written as separated ions˙Net ionic equation: only those compounds that undergo a change are written; spectator ions are not includedSolubility rules˙Based on experiment observation˙Help predict the outcomes of precipitation reactions
72 For Review ˙Important types of solution reactions Acid-base reactions: involve a transfer of H+ ions˙Precipitation reactions: formation of a solid occurs˙Oxidation-reduction reactions: involve electron transferTitrations˙Measures the volume of a standard solution (titrant) needed to react with a substance in solution˙Stoichiometric(equivalence)point: the point at which the required amount of titrant has been added to exactly react with the substance being analyzed˙Endpoint: the point at which a chemical indicator changes colorOxidation-reduction reactions˙Oxidation states are assigned using a set of rules to keep track of electron flow˙Oxidation: increase in oxidation state (a loss of electrons)˙Reduction: decrease in oxidation state (a gain of electrons)˙Oxidizing agent: gains electrons (is reduced)˙Reducing agent: loses electrons (is oxidized)˙Equaitons for oxidation—reduction reactions are usually balanced by the half-reaction method
73 Types of Chemical Reactions and Solution Stoichiometry Chapter FourTypes of Chemical Reactions and Solution Stoichiometry案例/討論
74 Figure 4.10a-c Steps Involved in the Preparation of a Standard Aqueous Solution
97 Aluminum and Iodine Mix to Form Aluminum Iodide
98 When Potassium Dichromate Reacts with Ethanol, the Solution Contains Cr3+.
99 Table 4.1 Simple Rules for the Solubility of Salts in Water
100 Table 4.2 Rules for Assigning Oxidation States
101 Types of Chemical Reactions and Solution Stoichiometry Chapter FourTypes of Chemical Reactions and Solution Stoichiometry問答/練習
102 QuestionWhich of the following solutions contains the greatest total ion concentration?One mole of potassium chloride dissolved in 1.0 L of solutionOne mole of iron(II) nitrate dissolved in 1.0 L of solutionOne mole of potassium hydroxide dissolved in 1.0 L of solutionOne mole of sodium phosphate dissolved in 1.0 L of solution
103 Answer d) One mole of sodium phosphate dissolved in 1.0 L of solution Section 4.2, The Nature of Aqueous Solutions: Strong and Weak ElectrolytesAll of the possible answers are strong electrolytes. The one that dissociates into the most ions [KCl into 2 mol ions, Fe(NO3)2 into 3 mol ions, KOH into 2 mol ions, Na3PO4 into 4 mol ions] is the answer.
104 Question Which of the following statements is true? If a substance is soluble, it must be an electrolyte.If a substance is an electrolyte, it must be soluble.Weak electrolytes must be less soluble than strong electrolytes.Nonelectrolytes are nonsoluble.
105 Answer b) If a substance is an electrolyte, it must be soluble. Section 4.2, The Nature of Aqueous Solutions: Strong and Weak ElectrolytesElectrolytes are substances that dissolve into ions. Not all soluble substances are electrolytes (such as table sugar).
106 QuestionConsider five solutions, each of which has the same mass of solute in mL of solution. Which has the highest concentration as measured in molarity?KClNaClNa2SO4NaFCaCl2
107 Answer d) NaF Section 4.3, The Composition of Solutions The highest concentration as measured in molarity for the same volume of solution will be determined by the solute with the smallest molar mass.
108 QuestionWhich of the following solutions contains the greatest number of ions?400.0 mL of 0.10 M NaCl300.0 mL of 0.10 M CaCl2200.0 mL of 0.10 M FeCl3800.0 mL of 0.10 M sucrose
109 Answerb) mL of 0.10 M CaCl2.Section 4.3, The Composition of SolutionsThe concentrations are all the same, so we must look at the volumes and the number of ions per compound. While each molecule of FeCl3 dissolves into four ions, and each molecule of CaCl2 dissolves into only three ions, the greater volume of the CaCl2 solution more than makes up for this difference.
110 QuestionLead(II) nitrate reacts with sodium chloride in aqueous solution to form a precipitate. What is the net ionic equation for this reaction?Pb2+(aq) + 2NO3–(aq) Pb(NO3)2(s)Na2+(aq) + Cl–(aq) NaCl(s)Pb2+(aq) + 2Cl–(aq) PbCl2(s)Na+(aq) + NO3–(aq) NaNO3(s)
111 Answer c) Pb2+(aq) + 2Cl–(aq) PbCl2(s) Section 4.5, Precipitation Reactions; Section 4.6, Describing Reactions in SolutionBoth of the reactants are strong electrolytes and completely break up into ions, but the product, lead(II) chloride, is a precipitate.
112 QuestionAqueous solutions of sodium sulfide and copper(II) chloride are mixed together. Which statement is correct?Both NaCl and CuS will precipitate from solution.No precipitate will form.Only CuS will precipitate from solution.Only NaCl will precipitate from solution.
113 Answer c) Only CuS will precipitate from solution. Section 4.5, Precipitation ReactionsBased on the simple rules for solubility of salts in water, sodium chloride will not form a precipitate while copper(II) sulfide will.
114 QuestionAn aqueous solution of barium nitrate reacts with an aqueous solution of sodium sulfate. Identify the solid and indicate its coefficient in the balanced equation.NaNO3; 1BaSO4; 1NaNO3; 2BaSO4; 2None of the above
115 Answer b) BaSO4; 1 Section 4.5, Precipitation Reactions Based on the simple rules for solubility of salts in water, barium sulfate will precipitate as a solid. The balanced equation isBa(NO3)2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaNO3(aq)
116 QuestionYou have separate aqueous solutions of NaOH and Ca(OH)2 with the same concentrations. You wish to neutralize an aqueous solution of HCl. Which basic solution would require more volume to neutralize the acid?The NaOH solution.The Ca(OH)2 solution.More information is needed to answer this question.
117 Answer a) The NaOH solution. Section 4.8, Acid–Base Reactions The basic solution requiring the greater volume to neutralize the acid is the one with the smaller number of hydroxide ions available to react with the hydrogen ions.
118 QuestionFor the reaction of sodium bromide with chlorine gas to form sodium chloride and bromine, what are the appropriate half-reactions? (ox = oxidation; re = reduction)ox: Cl2 + 2e– 2Cl–; re: 2Br– Br2 + 2e–ox: 2Br– Br2 + 2e–; re: Cl2 + 2e– 2Cl–ox: Cl + e– Cl–; re: Br Br+ + e–ox: 2Cl– Cl2 + 2e– ; re: Na+ + e– Na
119 Answer b) ox: 2Br– Br2 + 2e–; re: Cl2 + 2e– 2Cl– Section 4.9, Oxidation–Reduction Reactions; Section 4.10, Balancing Oxidation–Reduction EquationsThe conversion of bromide ion to bromine represents an oxidation, with the loss of two electrons. The conversion of chlorine to chloride ion represents a reduction, requiring two electrons.
120 Question How many of the following are oxidation–reduction reactions? i. PCl3 + Cl2 PCl5ii. Cu + 2AgNO3 Cu(NO3)2 + 2Agiii. CO2 + 2LiOH Li2CO3 + H2Oiv. FeCl2 + 2NaOH Fe(OH)2 + 2NaCla) 0 b) 1 c) 2 d) 4
121 Answer c) 2 Section 4.9, Oxidation–Reduction Reactions The answers include (i), where phosphorus undergoes an oxidation from +3 to +5 and chlorine undergoes a reduction from 0 to –1, and (ii), where copper undergoes an oxidation from 0 to +2 and silver undergoes a reduction from +1 to 0.
122 QuestionWhich of the following is not an oxidation–reduction reaction?A precipitation reaction.A reaction in which a metal reacts with a nonmetal.A combustion reaction.The reaction of a metal with an acid.All of the above are oxidation–reduction reactions.
123 Answer a) A precipitation reaction. Section 4.9, Oxidation–Reduction ReactionsIn a precipitation reaction, soluble ions combine to form an insoluble solid with the ions in their same oxidation states. The other possible answers involve elements (in the zero oxidation state) reacting to ions with nonzero charges.
124 QuestionWhat are the oxidation numbers of carbon in CO2 and CO32–, respectively?+2, +6+4, +6–4, –4–4, –6+4, +4
125 Answer e) +4, +4 Section 4.9, Oxidation–Reduction Reactions If the oxidation state of oxygen in the oxide is –2, the carbon must be +4 for the resulting CO2 to be neutral, and the carbon must be +4 for the CO32– to have a –2 charge on the ion.
126 Question Identify the type of unbalanced reaction Mg + HCl MgCl2 + H2 using the following choices:Precipitation reactionAcid–base reactionOxidation–reduction reactionCombustion reaction
127 Answer c) Oxidation–reduction reaction Section 4.9, Oxidation–Reduction ReactionsThis particular reaction involves an element changing into an ion and an ion changing into the element, both of which result in changes in the oxidation states of the species.
128 QuestionEach of the following results in a chemical reaction. Which of these is not an oxidation–reduction reaction?Methane gas is burned in air.Iodine crystals are added to an aqueous solution of silver nitrate.A piece of silver metal is placed in an aqueous solution of copper(II) nitrate.Chlorine gas is bubbled through an aqueous solution of sodium bromide.Aqueous solutions of lead(II) nitrate and sodium iodide are mixed together.
129 Answere) Aqueous solutions of lead(II) nitrate and sodium iodide are mixed together.Section 4.9, Oxidation–Reduction ReactionsChoice (e) describes a precipitation reaction. The other choices all include elements that become part of a compound.
130 QuestionWhich of the following compounds contains nitrogen with the highest oxidation number?NH3NO2NCl3N2NO
131 Answer b) NO2 Section 4.9, Oxidation–Reduction Reactions The oxidation states of nitrogen are as follows: NH3, –3; NO2, +4; NCl3, +3; N2, 0; NO, +2.
133 Chemical Impact Arrhenius A Man with Solutions (p.132) Science is a human endeavor, subject to frailtiesand governed by personalities, politics, and prejudices.One of the best illustrations of the often bumpy path ofThe advancement of scientific knowledge is the story ofSwedish chemist Svante Arrhenius.……Such a setbakc could have ended his scientific career, butArrhenius was a crusader; he was determined to see histheory thriumph. He promptly embarked on a politicalcampaign, enlisted the aid of several prominent scientists,to get his theory accepted.Ultimately, the ionic theory triumphed. Arrhenius’ fameSpread, and honors heaped on him, culminating in theNobel Prize in chemistry in Not one to rest on hislaurels., Arrhenius turned to new fields, including astronomy,He formulated a new theory that the solar system may haveCome into being through the collision of stars. His exceptionalVersatility led him to study the use of serums to fight disease,Energy resources and conservation, and the origin of life.
134 Chemical Impact: Tiny Laboratories (p.138) Labchip by Caliper Technologies (Palo Alto, CA), showing photolithographically etched fluid channels (in red). Channels are typically 70 µm wide and 10 µm deep. Photo Courtesy Caliper Technologies.
135 Chemical Impact Iron Zeros In On Pollution (p.156) (Chlorinated organic compound)
136 Chemical Impact : Pearly White (p.159) Ca5(PO4)3(OH)(Ca10(PO4)6(OH)2 because thereare two molecules in a unit cell.)瑭瓷牙本質牙髓牙齦牙骨質Carbamide Peroxide Teeth Whiteners:1:1 mixture of urea and hydrogen peroxide （H2O2）,glycerin (see next page), statnnate （SnO44-）,pyrophosphate salts (P2O7 4-, preservatives) andflavoring agents.
138 Chemical Impact : Aging: Does It Involve Oxidation (p.160) Wrinkles, susceptibility, subsequently, activated molecules,immune system, cell membrane, detrimental, irreplaceable,fall into this category.Vitamin E (anti-oxidant), red blood cell (RBC),superoxide dismutase (SOD, anti-oxidant), gerontology, rheumatoid arthritis, muscular dystrophy.
139 Superoxide dismutase (超氧化歧化酶) The enzyme superoxide dismutase (SOD, EC ), catalyzes thedismutation of superoxide into oxygen and hydrogen peroxide. As such, it is an important antioxidant defense in nearly all cells exposedto oxygen. One of the exceedingly rare exceptions isLactobacillus plantarum and related lactobacilli, which use adifferent mechanism.The SOD-catalysed dismutation of superoxide may be written with the following half-reactions :M (n+1)+ − SOD + O 2− → M n+ − SOD + O 2M n+ − SOD + O 2− + 2H + → M (n+1)+ − SOD + H2O2.where M = Cu (n=1) ; Mn (n=2) ; Fe (n=2) ; Ni (n=2).In this reaction the oxidation state of the metal cation oscillates between n and n+1