Chemical Reactions Introduction Prepare for Recitation November 17th ALEKS Objective 12 due November 15th ANGEL Quiz 12 November 17th Lecture 34 November 9th Lecture 35 November 11th Lecture 36 November 14th Read Ch 3 1 3 2 3 6 2 7 4 2 4 4 Additional Preparation BLB 3 1 64 BLB 4 24 39 Packet Reactions 1 11 Late Drop Deadline Friday November 11th CH110 FA11 SAS 1 Chemical Reactions Introduction KEY QUESTIONS THE BIG PICTURE How do you determine the outcome of a chemical reaction How do we balance chemical reactions What types of reactions have we already encountered Remember Chemistry deals with matter and its changes What forces drive reactions to occur spontaneously How can identifying spectator ions and writing net ionic equations help us predict reaction chemistry By the end of Today s Lecture you should know Reaction stiochiometry and balanced equations Combustion Decomposition Combination Precipitation and Neutralization reactions Net ionic equations and spectator ions CH110 FA11 SAS 2 Final Concepts You Should Know Chapter 3 Chemical Equations How do I balance a chemical equation What is the percent yield of a reaction Chapter 4 Chemical Reactions What are precipitation reactions What are metathesis reactions What are redox reactions in particular and what are oxidation numbers What are net ionic equations and spectator ions Chapter 5 Thermochemistry What is enthalpy and the enthalpy of a reaction What is heat of formation How do bond enthalpies relate to both of these What is Hess s Law Chapter 15 Chemical Equilibrium What is an equilibrium constant How do you use an ICE table to calculate equilibrium constants or concentrations What is LeCh tlier s principle CH110 FA11 SAS 3 Review Conservation of Mass Law of Conservation of Mass Chem 110 Example Complete combustion of pentane C5H12 8 O2 5 CO2 6 H2O If mass of reactants is 100g then the mass of products is what Reactants C H O atoms Products C H O atoms Not ringing a bell See Lecture 13 Chapter 3 Stoichiometry CH110 FA11 SAS 4 Balancing Chemical Equations When reactants and products are both given balanced reactions are written by changing the Four Easy Rules 1 Write the unbalanced equation correctly C2H4 O2 CO2 H2O 2 Balance the atoms of one element C2H4 O2 CO2 H2O 3 Balance atoms of remaining elements C2H4 O2 CO2 H2O 4 Check your work CH110 FA11 SAS 5 Practice Problem Acid rain destroys marble sculptures and buildings If a statue loses 30 g of marble CaCO3 how many moles of calcium nitrate are washed away with the rain HNO3 aq CO2 g A B C D E CaCO3 s H2O l Ca NO3 2 aq 0 15 mols 0 30 mols 0 45 mols 1 50 mols 3 00 mols CH110 FA11 SAS 6 Simple Reaction Types Complete Combustion organic compound O2 C2H5OH l 3 O2 2 CO2 3 H2O Combination elements react to form compounds S s O2 g SO2 g 2Mg s O2 g 2 MgO s small compounds combine to make larger ones BF3 g NH3 g BF3NH3 g Decomposition 2 H 2 O 2 H 2 O2 H2CO3 H2O CO2 CaCO3 CaO CO2 Single Displacement Reactions CuSO4 aq Zn s ZnSO4 aq Cu s CH110 FA11 SAS 7 Practice Problems Use the patterns of reactivity to write balanced reactions for A The combustion of ethanol CH3CH2OH B The decomposition of lead carbonate C The combination of nitrogen and hydrogen to form ammonia NH3 CH110 FA11 SAS 8 Metathesis Reactions Double Displacement Reactions A very diverse set of reactions also known as or reactions Double displacement reactions only occur if there is a driving force such as 1 Precipitation CaCl2 aq Hg NO3 2 aq HgCl2 s Ca NO3 2 aq 2 Neutralization Acid Base HNO3 KOH H2O KNO3 3 Gas Formation 2HCl aq Na2S aq H2S g 2NaCl aq CH110 FA11 SAS 9 Demo Precipitation Reactions Use solubility rules to predict reactions based on the reactants provided Precipitation drives the reaction Mix AgNO3 and NaCl What happens 1 Form an ionic equation from the molecular equation Hypothesis 1 Hypothesis 2 CH110 FA11 SAS 10 Demo Precipitation Reactions Case 1 If NaNO3 is insoluble addition of NaCH3COO should result in precipitation too Ag NO3 Na CH3COO Case 2 If AgCl is insoluble addition of MgCl2 should result in precipitation too Ag NO3 Mg2 Cl Double Replacement Reaction Observed CH110 FA11 SAS 11 Aqueous Solubility of Ionic Compounds Simplified rules for solubility in water 1 Almost all ammonium and alkali metal salts are soluble 2 Most nitrates acetates halides and sulfates are soluble exception Ag Hg and Pb halides are insoluble exception Ca Ba and Pb sulfates are insoluble 3 Most sulfides carbonates phosphates and hydroxides are insoluble exception Rule 1 wins CH110 FA11 SAS 12 Spectator Ions and Net Ionic Equations Knowledge of what reactions are actually occurring requires us to figure out what is actually important in the Complete Ionic Equation Pb2 aq 2 NO3 aq 2 K aq 2 I aq PbI2 s 2 K aq 2 NO3 aq Spectator ions Ions that do not participate in the reaction are eliminated from the Net Ionic Equation CH110 FA11 SAS 13 Practice Problems Mixing solutions of K2SO4 aq and BaCl2 aq produces an insoluble salt What is the identity of the spectator ions A B C D E K SO42 Ba2 ClK SO42K ClBa2 ClBa2 SO42 Mixing solutions of CaCl2 aq and AgNO3 aq produces an insoluble salt What is the identity of the precipitant A B C D E Ca NO3 2 s Ca2 NO3Ag ClAgCl s Ca2 Cl Ag NO3CH110 FA11 SAS 14 Neutralization Reactions Acids Bases and Salts Acids hydrogen ion H aq Bases hydrogen ion Raise concentration of OH aq ions Salts Ionic compounds of acid with positive ion e g HNO3 becomes KNO3 CH110 FA11 SAS 15 Hydrogen Ion Transfer Water plays a very special role in acidbase chemistry Dissolving bases in water increases the Not all acids and bases are ionic CH110 FA11 SAS 16 Acid Base Neutralization ACID BASE SALT WATER HNO3 KOH KNO3 H2O complete H aq NO3 aq K aq OH aq ionic equation H2O l K aq NO3 aq eliminate spectator ions net ionic equation of the acid and base drives the reaction CH110 FA11 SAS 17 Practice Problem What is the net ionic equation for the reaction between sodium hydroxide and acetic acid A B C D E CH3COOH aq OH CH3COO H2O H OH H2O Na CH3COO aq NaCH3COO s CH3COOH aq Na NaCH3COO aq H CH3COOH aq Na OH CH3COO H2O Na CH110 FA11 SAS 18 Practice Problem What is the net ionic equation for the reaction between sodium hydroxide and sulfuric acid A 2Na aq SO42 aq Na2SO4 s B 2H aq 2OH aq 2H2O C Na aq OH aq H aq HSO4 aq H2O Na aq HSO4 aq D OH aq H2SO4 aq H2O HSO4 aq E 2 Na aq 2 OH aq 2 H aq SO42 aq 2 H2O 2 Na aq SO42 aq CH110 FA11 SAS 19 What You Should Know Reaction Stoichiometry What do the coefficients and subscripts in a
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