* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 4
Hydrogen-bond catalysis wikipedia , lookup
Transition state theory wikipedia , lookup
Electrolysis of water wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Oxidation state wikipedia , lookup
Click chemistry wikipedia , lookup
Acid dissociation constant wikipedia , lookup
Nucleophilic acyl substitution wikipedia , lookup
Chemical reaction wikipedia , lookup
Stoichiometry wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Metalloprotein wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Acid–base reaction wikipedia , lookup
Electrochemistry wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Chapter 4 Types of Chemical Reactions and Solution Stoichiometry Chapter 4 Table of Contents • • • Precipitation Reactions Acid–Base Reactions Oxidation–Reduction Reactions Copyright © Cengage Learning. All rights reserved 3 Section 4.1 Water, the Common Solvent • • • One of the most important substances on Earth. Can dissolve many different substances. A polar molecule because of its unequal charge distribution. Return to TOC Copyright © Cengage Learning. All rights reserved 4 Section 4.1 Water, the Common Solvent Dissolution of a Solid in a Liquid Return to TOC Copyright © Cengage Learning. All rights reserved 5 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Nature of Aqueous Solutions • • • Solute – substance being dissolved. Solvent – liquid water. Electrolyte – substance that when dissolved in water produces a solution that can conduct electricity. Return to TOC Copyright © Cengage Learning. All rights reserved 6 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Nonelectrolytes: -dissolves in water, produces no ions -most molecular compounds don’t dissociate in water. -no current flows -”like dissolves like” Ex: sugar, methanol Weak electrolytes: -weak acids and bases have some dissociation -conduct only a small current Ex: CH3COOH(aq)↔ H+(aq) + CH3COO-(aq) NH3(aq) + H2O(aq) ↔ NH4+(aq) + OH-(aq) Strong electrolytes: -soluble salts, strong acids, & strong bases have complete dissociation -conduct current very efficiently Ex: NaCl(aq) ↔ Na+(aq) + Cl-(aq) HCl(aq) ↔ H+(aq) + Cl-(aq) NaOH(aq) ↔ Na+(aq) + OH-(aq) Return to TOC 7 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Good Time to Review Strong Acids…… STRONG ACIDS Return to TOC Copyright © Cengage Learning. All rights reserved 8 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Lets Review Strong Bases Now…. Notice Group 1A are all soluble with OHIn Group 2A are all soluble except Mg+2 Return to TOC Copyright © Cengage Learning. All rights reserved 9 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Electrolyte Behavior Return to TOC Copyright © Cengage Learning. All rights reserved 10 Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Electrolyte Behavior • Smaller ions have stronger electric field so they drag more water molecules around with them. Return to TOC Copyright © Cengage Learning. All rights reserved 11 Section 4.3 The Composition of Solutions Chemical Reactions of Solutions We must know: The nature of the reaction. Is it acid-base rxn, ppt rxn, etc. The amounts of chemicals present in the solutions. How much solute is in the solvent. Return to TOC Copyright © Cengage Learning. All rights reserved 12 Section 4.3 The Composition of Solutions Chemistry Humor…… Return to TOC Copyright © Cengage Learning. All rights reserved 13 Section 4.3 The Composition of Solutions Molarity • Molarity (M) = moles of solute per volume of solution in liters: M = Molarity = moles of solute liters of solution 6 moles of HCl 3 M HCl = 2 liters of solution mass/molar mass M = Molarity = liters of solution Return to TOC Copyright © Cengage Learning. All rights reserved 14 Section 4.3 The Composition of Solutions Molarity • Intensive property: Independent on amount In my prep room I have 1 liters of a 6M HCl solution If I take 50ml of this solution, it is still 6M • Temperature dependent Solutions expand & contract w/temp. So, volume of the solution will change Return to TOC Copyright © Cengage Learning. All rights reserved 15 Section 4.3 The Composition of Solutions Concentration of Ions • For a 0.25 M CaCl2 solution: CaCl2 → Ca2+ + 2Cl– Ca2+: 1 × 0.25 M = 0.25 M Ca2+ Cl–: 2 × 0.25 M = 0.50 M Cl–. Return to TOC Copyright © Cengage Learning. All rights reserved 17 Section 4.3 The Composition of Solutions Concept Check Which of the following solutions contains the greatest number of ions? a) b) c) d) 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. Return to TOC Copyright © Cengage Learning. All rights reserved 18 Section 4.3 The Composition of Solutions Notice • The 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. Return to TOC Copyright © Cengage Learning. All rights reserved 20 Section 4.3 The Composition of Solutions Dilution • • • The process of adding water to a concentrated or 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 dilution M1V1 = M2V2 Return to TOC Copyright © Cengage Learning. All rights reserved 21 Section 4.4 Types of Chemical Reactions • • • Precipitation Reactions Acid–Base Reactions Oxidation–Reduction Reactions Return to TOC Copyright © Cengage Learning. All rights reserved 24 Section 4.5 Precipitation Reactions 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 ions. Precipitate – the solid that forms. Return to TOC Copyright © Cengage Learning. All rights reserved 25 Section 4.5 Precipitation Reactions The Reaction of K2CrO4(aq) and Ba(NO3)2(aq) • Ba2+(aq) + CrO42–(aq) → BaCrO4(s) Return to TOC Copyright © Cengage Learning. All rights reserved 26 Section 4.5 Precipitation Reactions Precipitation of Silver Chloride Return to TOC Copyright © Cengage Learning. All rights reserved 27 Section 4.5 Precipitation Reactions Precipitates • • • Soluble – solid dissolves in solution; (aq) is used in reaction. Insoluble – solid does not dissolve in solution; (s) is used in reaction. Insoluble and slightly soluble are often used interchangeably. Return to TOC Copyright © Cengage Learning. All rights reserved 28 Section 4.5 Precipitation Reactions Simple Rules for Solubility 1. Most nitrate (NO3) salts are soluble. 2. Most alkali metal (group 1A) salts and NH4+ are soluble. 3. Most Cl, Br, and I salts are soluble (except Ag+, Pb2+, Hg22+). 4. Most sulfate salts are soluble (except BaSO4, PbSO4, Hg2SO4, CaSO4). 5. Most OH are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble). 6. Most S2, CO32, CrO42, PO43 salts are only slightly soluble, except for those containing the cations in Rule 2. Copyright © Cengage Learning. All rights reserved Return to TOC 29 Section 4.5 Precipitation Reactions Concept Check Which of the following ions form compounds with Pb2+ that are generally soluble in water? a) b) c) d) e) S2– Cl– NO3– SO42– Na+ Return to TOC Copyright © Cengage Learning. All rights reserved 30 Section 4.6 Describing Reactions in Solution Formula Equation (Molecular Equation) • • • Gives the overall reaction stoichiometry but not necessarily the actual forms of the reactants and products in solution. Reactants and products generally shown as compounds. Use solubility rules to determine which compounds are aqueous and which compounds are solids. AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) Return to TOC Copyright © Cengage Learning. All rights reserved 31 Section 4.6 Describing Reactions in Solution Complete Ionic Equation • Represents as ions all reactants and products that are strong electrolytes. Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq) AgCl(s) + Na+(aq) + NO3(aq) Return to TOC Copyright © Cengage Learning. All rights reserved 32 Section 4.6 Describing Reactions in Solution Net Ionic Equation • Includes only those solution components undergoing a change. Show only components that actually react. Ag+(aq) + Cl(aq) AgCl(s) • Spectator ions are not included (ions that do not participate directly in the reaction). Na+ and NO3 are spectator ions. Return to TOC Copyright © Cengage Learning. All rights reserved 33 Section 4.6 Describing Reactions in Solution Concept Check Write the correct formula equation, complete ionic equation, and net ionic equation for the reaction between cobalt(II) chloride and sodium hydroxide. Formula Equation: CoCl2(aq) + 2NaOH(aq) Co(OH)2(s) + 2NaCl(aq) Complete Ionic Equation: Co2+(aq) + 2Cl(aq) + 2Na+(aq) + 2OH(aq) Co(OH)2(s) + 2Na+(aq) + 2Cl(aq) Net Ionic Equation: Co2+(aq) + 2Cl(aq) Co(OH)2(s) Copyright © Cengage Learning. All rights reserved Return to TOC 34 Section 4.7 Stoichiometry of Precipitation Reactions Solving Stoichiometry Problems for Reactions in Solution 1. Identify the species present in the combined solution, and determine what reaction if any occurs. 2. Write the balanced net ionic equation for the reaction. 3. Calculate the moles of reactants. 4. Determine which reactant is limiting. 5. Calculate the moles of product(s), as required. 6. Convert to grams or other units, as required. Return to TOC Copyright © Cengage Learning. All rights reserved 35 Section 4.7 Stoichiometry of Precipitation Reactions Concept Check (Part I) 10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change). What precipitate will form? lead(II) phosphate, Pb3(PO4)2 What mass of precipitate will form? 1.1 g Pb3(PO4)2 Return to TOC Copyright © Cengage Learning. All rights reserved 36 Section 4.7 Stoichiometry of Precipitation Reactions Let’s Think About It • Where are we going? • To find the mass of solid Pb3(PO4)2 formed. How do we get there? What are the ions present in the combined solution? What is the balanced net ionic equation for the reaction? What are the moles of reactants present in the solution? Which reactant is limiting? What moles of Pb3(PO4)2 will be formed? What mass of Pb3(PO4)2 will be formed? Return to TOC Copyright © Cengage Learning. All rights reserved 37 Section 4.7 Stoichiometry of Precipitation Reactions Concept Check (Part II) 10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change). What is the concentration of nitrate ions left in solution after the reaction is complete? 0.27 M Return to TOC Copyright © Cengage Learning. All rights reserved 38 Section 4.7 Stoichiometry of Precipitation Reactions Let’s Think About It • Where are we going? • To find the concentration of nitrate ions left in solution after the reaction is complete. How do we get there? What are the moles of nitrate ions present in the combined solution? What is the total volume of the combined solution? Return to TOC Copyright © Cengage Learning. All rights reserved 39 Section 4.7 Stoichiometry of Precipitation Reactions Concept Check (Part III) 10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change). What is the concentration of phosphate ions left in solution after the reaction is complete? 0.011 M Return to TOC Copyright © Cengage Learning. All rights reserved 40 Section 4.7 Stoichiometry of Precipitation Reactions Let’s Think About It • Where are we going? • To find the concentration of phosphate ions left in solution after the reaction is complete. How do we get there? What are the moles of phosphate ions present in the solution at the start of the reaction? How many moles of phosphate ions were used up in the reaction to make the solid Pb3(PO4)2? How many moles of phosphate ions are left over after the reaction is complete? What is the total volume of the combined solution? Copyright © Cengage Learning. All rights reserved Return to TOC 41 Section 4.8 Acid–Base Reactions Acid–Base Reactions (Brønsted–Lowry) • • • Acid—proton donor Base—proton acceptor For a strong acid and base reaction: H+(aq) + OH–(aq) H2O(l) Return to TOC Copyright © Cengage Learning. All rights reserved 42 Section 4.8 Acid–Base Reactions Neutralization of a Strong Acid by a Strong Base Return to TOC Copyright © Cengage Learning. All rights reserved 43 Section 4.8 Acid–Base Reactions Performing Calculations for Acid–Base Reactions 1. List the species present in the combined solution before any reaction occurs, and decide what reaction will occur. 2. Write the balanced net ionic equation for this reaction. 3. Calculate moles of reactants. 4. Determine the limiting reactant, where appropriate. 5. Calculate the moles of the required reactant or product. 6. Convert to grams or volume (of solution), as required. Copyright © Cengage Learning. All rights reserved Return to TOC 44 Section 4.8 Acid–Base Reactions Acid–Base Titrations • • • Titration – delivery of a measured volume of a solution of known concentration (the titrant) into a solution containing the substance being analyzed (the analyte). Equivalence point – enough titrant added to react exactly with the analyte. Endpoint – the indicator changes color so you can tell the equivalence point has been reached. Return to TOC Copyright © Cengage Learning. All rights reserved 45 Section 4.8 Acid–Base Reactions Concept Check For the titration of sulfuric acid (H2SO4) with sodium hydroxide (NaOH), how many moles of sodium hydroxide would be required to react with 1.00 L of 0.500 M sulfuric acid to reach the endpoint? 1.00 mol NaOH Return to TOC Copyright © Cengage Learning. All rights reserved 46 Section 4.8 Acid–Base Reactions Let’s Think About It • Where are we going? • To find the moles of NaOH required for the reaction. How do we get there? What are the ions present in the combined solution? What is the reaction? What is the balanced net ionic equation for the reaction? What are the moles of H+ present in the solution? How much OH– is required to react with all of the H+ present? Return to TOC Copyright © Cengage Learning. All rights reserved 47 Section 4.9 Oxidation–Reduction Reactions Redox Reactions • Reactions in which one or more electrons are transferred. Return to TOC Copyright © Cengage Learning. All rights reserved 48 Section 4.9 Oxidation–Reduction Reactions Reaction of Sodium and Chlorine Return to TOC Copyright © Cengage Learning. All rights reserved 49 Section 4.9 Oxidation–Reduction Reactions Rules for Assigning Oxidation States 1. Oxidation state of an atom in an element = 0 2. Oxidation state of monatomic ion = charge of the ion 3. Oxygen = 2 in covalent compounds (except in peroxides where it = 1) 4. Hydrogen = +1 in covalent compounds 5. Fluorine = 1 in compounds 6. Sum of oxidation states = 0 in compounds 7. Sum of oxidation states = charge of the ion in ions Return to TOC Copyright © Cengage Learning. All rights reserved 50 Section 4.9 Oxidation–Reduction Reactions Exercise Find the oxidation states for each of the elements in each of the following compounds: • • • • • K2Cr2O7 CO32MnO2 PCl5 SF4 K = +1; Cr = +6; O = –2 C = +4; O = –2 Mn = +4; O = –2 P = +5; Cl = –1 S = +4; F = –1 Return to TOC Copyright © Cengage Learning. All rights reserved 51 Section 4.9 Oxidation–Reduction Reactions Redox Characteristics • • • • Transfer of electrons Transfer may occur to form ions Oxidation – increase in oxidation state (loss of electrons); reducing agent Reduction – decrease in oxidation state (gain of electrons); oxidizing agent Return to TOC Copyright © Cengage Learning. All rights reserved 52 Section 4.9 Oxidation–Reduction Reactions Concept Check Which 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) Return to TOC Copyright © Cengage Learning. All rights reserved 53 Section 4.10 Balancing Oxidation–Reduction Equations Balancing Oxidation–Reduction Reactions by Oxidation States 1. Write the unbalanced equation. 2. Determine the oxidation states of all atoms in the reactants and products. 3. Show electrons gained and lost using “tie lines.” 4. Use coefficients to equalize the electrons gained and lost. 5. Balance the rest of the equation by inspection. 6. Add appropriate states. Copyright © Cengage Learning. All rights reserved Return to TOC 54 Section 4.10 Balancing Oxidation–Reduction Equations • Balance the reaction between solid zinc and aqueous hydrochloric acid to produce aqueous zinc(II) chloride and hydrogen gas. Return to TOC Copyright © Cengage Learning. All rights reserved 55 Section 4.10 Balancing Oxidation–Reduction Equations 1. What is the unbalanced equation? • Zn(s) + HCl(aq) Zn2+(aq) + Cl–(aq) + H2(g) Return to TOC Copyright © Cengage Learning. All rights reserved 56 Section 4.10 Balancing Oxidation–Reduction Equations 2. What are the oxidation states for each atom? • Zn(s) + HCl(aq) Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0 Return to TOC Copyright © Cengage Learning. All rights reserved 57 Section 4.10 Balancing Oxidation–Reduction Equations 3. How are electrons gained and lost? 1 e– gained (each atom) • Zn(s) + HCl(aq) Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0 2 e– lost • The oxidation state of chlorine remains unchanged. Return to TOC Copyright © Cengage Learning. All rights reserved 58 Section 4.10 Balancing Oxidation–Reduction Equations 4. What coefficients are needed to equalize the electrons gained and lost? 1 e– gained (each atom) × 2 • Zn(s) + HCl(aq) Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0 2 e– lost • Zn(s) + 2HCl(aq) Zn2+(aq) + Cl–(aq) + H2(g) Return to TOC Copyright © Cengage Learning. All rights reserved 59 Section 4.10 Balancing Oxidation–Reduction Equations 5. What coefficients are needed to balance the remaining elements? • Zn(s) + 2HCl(aq) Zn2+(aq) + 2Cl–(aq) + H2(g) Return to TOC Copyright © Cengage Learning. All rights reserved 60 Section 4.10 Balancing Oxidation–Reduction Equations Chemical Reactions: Reactions can actually be categorized in the following 3 main groupings: 1) The Precipitation 2) The Redox 3) The Acid/Base Synthesis and Decomposition (special case acid/base OR redox) Return to TOC Section 4.10 The Precipitation Balancing Oxidation–Reduction Equations 1 2 3 Look at Cation Anion Anion Is it a(an): Then the compound is Alkali metal(Grp IA) or ammonium Nitrate, acetate, or perchlorate Halide SOLUBLE SOLUBLE SOLUBLE Except: Ag+, Hg22+, Pb2+ SOLUBLE Except: Ba2+, Hg2+, Pb2+, Ca2+ INSOLUBLE Except: Rule 1 INSOLUBLE Except: Rule 1 Likely INSOLUBLE 4 Anion Sulfate 5 6 Anion Hydroxide (Mg and Ca are slightly soluble) Anion Sulfide, carbonate, phosphate 7 Cation If you get this far, the compound is Ex: Solutions of copper(II) nitrate and sodium phosphate are mixed 3Cu2+ + 2PO 3- Cu (PO ) 4 3 42 Return to TOC Section 4.10 The Precipitation: Now You Try Balancing Oxidation–Reduction Equations Aqueous solutions of silver nitrate and sodium chloride are mixed, resulting in the formation of a precipitate in a solution. Ag+ + Cl- AgCl Solutions of nickel(II) acetate and potassium hydroxide are mixed, resulting in visible precipitation in the solution. Ni2+ + 2OH- Ni(OH) 2 Solutions of iron(III) chloride and lithium carbonate are mixed, resulting in a visible precipitate in a solution. 2Fe3+ + 3CO 2- Fe (CO ) 3 2 33 Return to TOC Section 4.10 Redox #1 Balancing Oxidation–Reduction Equations 1) Single replacement Magnesium metal is placed in a solution of iron(III) chloride 3Mg + 2 Fe3+ 3Mg2+ + 2Fe Solid potassium is added to distilled water 2K + 2H2O 2K+ + 2OH- + H2 Solutions of fluorine and sodium chloride are mixed F2 + 2 Cl- 2F- + Cl2 Return to TOC Section 4.10 Redox #1: Now You Try Balancing Oxidation–Reduction Equations A solution of silver nitrate is poured over copper metal 2Ag+ + Cu 2Ag + Cu2+ Cadmium metal is placed in a solution of tin(II) chloride Sn2+ + Cd Cd2+ + Sn A solution of sodium iodide is place in bromine water 2I- + Br 2 I + 2Br2 Solutions of tin(II) chloride and iron(III) chloride are mixed Sn2+ + 2Fe3+ Sn4+ + 2Fe2+ Return to TOC Section 4.10 Balancing Oxidation–Reduction Equations Redox #2 Combustion butanol (C4H10O) is burned in air C4H10O + 6 O2 4 CO2 + 5 H2O calcium is burned in air 2Ca + O2 2CaO Return to TOC Section 4.10 Redox #2: Now You Try Balancing Oxidation–Reduction Equations Propane (C H ) is burned in air 3 8 C H + 5O 3 CO + 4H O 3 8 2 2 2 Ethyne (C H ) is burned in air 2 2 2C H + 5O 4CO + 2H O 2 2 2 2 2 Magnesium metal is burned in air 2Mg + O 2 2MgO Return to TOC Section 4.10 Synthesis and Decomposition As Redox Now You Try Balancing Oxidation–Reduction Equations Hydrogen peroxide is left in light 2H O O + 2H O 2 2 2 2 Lithium metal is strongly heated in nitrogen gas 3Li + N 2Li N 2 3 Molten sodium chloride is electrolyzed 2Na+ + 2Cl- 2Na + Cl 2 Aqueous sodium iodide is electrolyzed 2H O + 2I- H + 2OH- + I 2 2 2 Return to TOC Section 4.10 Acid/Base: Balancing Oxidation–Reduction Equations Bronsted Lowry: H+ transfer 1) Traditional: Solutions of ethanoic (CH COOH) acid and sodium hydroxide are mixed 3 H O + CH COOCH COOH + OH3 2 3 Look for stoichiometry “excess” or “equal volumes of equimolar” A) equal volumes of equimolar solutions of sodium phosphate and hydrochloric acid are mixed H+ + PO 3- HPO 24 4 to aqueous sodium phosphate B) excess hydrochloric acid is added 3H+ + PO 3 H PO 4 3 4 Return to TOC Acid/Base: Now You Try Section 4.10 Balancing Oxidation–Reduction Equations Solutions of hydrochloric acid and sodium hydroxide are mixed H+ + OH- H O 2 Hydroiodic acid is poured over solid calcium carbonate 2H+ + CaCO Ca2+ + H O + CO 3 2 2 A solution of nitric acid was poured into an ammonia solution H+ + NH 3 NH + 4 Solutions of nitrous acid and potassium hydroxide are mixed HNO + OH- H O + NO 2 2 2 Solutions of hydrofluoric acid and methylamine are mixed HF + CH NH CH NH + + F3 2 3 3 20. mL of 0.10 M hydrochloric acid is mixed with 5.0 mL of 0.2 M sodium phosphate 2H+ + PO 3- H PO 4 2 4 Return to TOC Section 4.10 Final Thoughts Balancing Oxidation–Reduction Equations When information is given pertaining to reactivity, a reaction ALWAYS occurs. Use checklist approach to categorize reaction type Remember unstable acids: H CO , H SO 2 3 2 3 and NH OH 4 Sulfuric acid appears as either: H+ + HSO - (sometimes 2H+ + SO 2-) 4 4 Return to TOC