Reactions Chapter 3 Combustion Decomposition Combination Chapter 4 Reactions Exchange reactions Metathesis Formation of a precipitate Formation of a gas Formation of a week or nonelectrolyte Single Displacement Reactions Redox reactions Oxidation numbers Mary J Bojan Chem 110 1 Balancing Equations Law of conservation of mass matter cannot be lost in any chemical reaction Mary J Bojan Chem 110 2 Patterns of reactivity Know how to balance a chemical reaction Complete p Combustion reactions Chapter p 3 C3H8 g 5O2 g 3CO2 g 4H2O g Combination reactions Chapter 3 2Mg s O2 2MgO s Decomposition reactions Chapter C 3 PbCO3 s PbO s CO2 g Mary J Bojan Chem 110 3 Write balanced reactions for The combustion of ethanol CH3CH2OH The decomposition of lead carbonate PbCO3 The combination of nitrogen and hydrogen to form ammonia NH3 Mary J Bojan Chem 110 4 Patterns of reactivity K Know h how to t balance b l a chemical h i l reaction ti Exchange reactions Chapter 4 P Precipitation i it ti Pb NO3 2 aq 2KI aq PbI s 2KNO3 aq Neutralization NaOH aq HCl aq NaCl aq H2O Gas formation 2HCl aq Na2S aq H2S g 2NaCl aq Single displacement reactions Chapter 4 O2 g 2CaO s 2Ca s Mary J Bojan Chem 110 5 Exchange reaction Double Displacement Exchange positive ions to get products AD XZ AZ XD Example R Reactants t t Pb NO3 2 KI Balance the reaction D Does anything thi happen h TRY Do y you have to do the reaction to know Mary J Bojan Chem 110 6 Metathesis Reactions Double Displacement Given reactants exchange positive ions to get products Requires a driving force otherwise nothing happens D i i Forces Driving F 1 2 3 Precipitate forms Weak or nonelectrolyte forms Gas forms How do you know what is happening Net Ionic Equation Mary J Bojan Chem 110 7 Precipitation Reaction Mix silver nitrate and sodium chloride What happens Molecular Equation Ionic Equation Spectator ions Net Ionic Equation Mary J Bojan Chem 110 8 SOLUBILITY RULES FOR COMMON IONIC COMPOUNDS IN WATER 1 Almost all ammonium and alkali metal salts are soluble 2 Most nitrates acetates chlorides bromides and sulfates are soluble Exceptions p silver halides sulfates of Ca Ba Pb Ag 3 Most sulfides 3 sulfides carbonates carbonates phosphates and hydroxides are insoluble Exceptions alkali salts ammonium salts See 1 above See Table 4 1 of Brown LeMay and Bursten for a more comprehensive listing Mary J Bojan Chem 110 9 Formation of Weak or Nonelectrolyte neutralization reaction Acid base salt water Molecular Equation Ionic Equation Spectator ions Net Ionic Equation Mary J Bojan Chem 110 10 Practice What is the net ionic equation for the reaction between sodium hydroxide and acetic acid What is the net ionic equation for the reaction between sodium chloride and potassium iodide Mary J Bojan Chem 110 11 GAS FORMATION Direct Di t production d ti off a gas CO2 H2S S NO2 SO2 Production of weak acid which decomposes Example Molecular Equation NaHCO3 aq HCl aq H2CO3 aq NaCl aq CO2 g H2O l Ionic Equation Na aq HCO3 aq H aq Cl aq H2CO3 aq aq Na aq Cl aq Na aq Cl aq CO2 g H2O l Net Ionic Equation H aq HCO3 aq CO2 g H2O l Mary J Bojan Chem 110 12 Single Displacement reactions Oxidation Reduction Oxidation Reduction Zn s CuSO4 aq ZnSO4 aq Cu s What is oxidized What is reduced What is the oxidizing agent What is the reducing agent Ionic equation Net ionic equation Mary J Bojan Chem 110 13 Rules for determining Oxidation States 1 2 3 4 5 Oxidation state of atom in elemental form is zero e g Cl2 O2 P4 C s S8 The oxidation number of a monatomic ion equals its charge Some elements have common oxidation numbers that can be used as reference in determining the oxidation numbers of other atoms in the compound Alkali metals 1 Alkaline earth metals 2 Fluorine 1 H usually 1 Hydrides metal H compounds 1 O usually 2 peroxides 1 superoxides possible Cl Br I almost always 1 Sum of oxidation numbers is equal to overall charge of molecule or ion For a neutral compound the sum of oxidation numbers equals zero For a polyatomic ion ion the sum of the oxidation numbers is equal to the charge on the ion Shared electrons are assigned to the more electronegative atom of the pair more electronegative atom will have a negative oxidation number number Mary J Bojan Chem 110 14 ActivitySeries Table 4 5 Will the metal element displace the atom from its compound in a reaction Na s H2O l Au s H2O g g Zn s AgNO3 aq Active metals groups IA IIA Al very reactive I Inactive ti inert i t metals t l jewelry j l metals t l Do D nott reactt readily dil Other metals in between Mary J Bojan Chem 110 15 Reactions Stoichiometry Solving problems involving Chemical reactions Limiting Reactants Solution reactions G phase Gas h reactions i Mary J Bojan Chem 110 16 Basics before you start Assume you know Avogadro s number memorize i it definition of mole Formula weight g molar mass the following connections or conversions gram mole gram molecules what is meant by Use these along with the empirical i i l formula f l balanced chemical molecular formula reaction to solve problems in chemistry p y Mary J Bojan Chem 110 17 How to solve problems write the balanced chemical reaction or process make connections between experimentally measured properties and the balanced equation In other words Given information such as mass volume pressure and temperature how can one determine quantities of temperature moles molecules Mary J Bojan Chem 110 18 IMPORTANT CONNECTIONS Avogadro s number C Connects t molecules l l or atoms t to t moles l Connects microscopic properties to macroscopic properties Conservation of Mass Mass of Products Mass of reactants Balance the reaction Balanced Chemical Equation Connects moles molecules of reactants with moles molecules of products Related to conservation of Mass Formula weight Connects mass to moles Connects a property that can be measured determined experimentally to moles or molecules of substance given in the balanced reaction Empirical Formula Tells relative number of atoms in a molecule Obtained from mass or molecular formula Mary J Bojan Chem 110 19 Problem Solving 1 Write balanced chemical equation 1 2 Make a table Fill in given information 3 Note connections between measured quantities titi and d moles l Mass Volume solutions P V T gases M W moles concentration moles ideal gas law moles 4 Fill in table until you are able to solve the problem 5 Make sure your answer is REASONABLE 6 TRY things 6 Mary J Bojan Chem 110 20 Sample Problems Methane reacts with water to produce hydrogen gas and
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