Chemical Reactions Classification - Chapter Five - PDF

Abdullah Al Noumas Learning topic Chemical Reactions: Classification Fundamentals of General, Organic and Biological Chemistry Chapter Five  Outline ► 5.3 Classes of Chemical Reactions ► 5.4 Precipitation Reactions and Solubil...

Abdullah Al Noumas Learning topic Chemical Reactions: Classification Fundamentals of General, Organic and Biological Chemistry Chapter Five  Outline ► 5.3 Classes of Chemical Reactions ► 5.4 Precipitation Reactions and Solubility Guidelines ► 5.5 Acids, Bases, and Neutralization Reactions ► 5.6 Redox Reactions ► 5.7 Recognizing Redox Reactions ► 5.8 Net Ionic Equations Copyright © 2010 Pearson Education, Inc. Chapter Six 2  5.3 Classes of Chemical Reactions ► When learning about chemical reactions it is helpful to group the reactions of ionic compounds into three general classes: precipitation reactions, acid–base neutralization reactions, and oxidation–reduction reactions. ► Precipitation reactions are processes in which an insoluble solid called a precipitate forms when reactants are combined in aqueous solution. ex KzC03 t USG Kzs t 03 aq aq qq s Copyright © 2010 Pearson Education, Inc. Chapter Six 3 ex Acid Base Salt water HCl NaOH Nacl H2o ► Acid–base neutralization reactions are processes in which H+ ions from an acid react with OH- ions from a base to yield water. An ionic compound called a salt is also produced. The “salt” produced need not be common table salt. Any ionic compound produced in an acid–base reaction is called a salt. pus JUDD g III g reactions, or redox ► Oxidation–reduction reactions, are processes in which one or more electrons are transferred between reaction partners (atoms, molecules, or ions). As a result of this transfer, the charges on atoms in the various reactants change. ex Cat 2A Copyright © 2010 Pearson Education, Inc. EIAg Chapter Six 4  ZE 5.4 Precipitation Reactions and Solubility Guidelines ► Reaction of aqueous Pb(NO3)2 with aqueous KI gives a yellow precipitate of PbI2. ► To predict whether a precipitation reaction will occur on mixing aqueous solutions of two ionic compounds, you must know the solubility of the potential products. Copyright © 2010 Pearson Education, Inc. Chapter Six 5  If a potential product does not contain at least one of the ions listed below, it is probably not soluble and will precipitate from solution when formed. LabManual t insoluble Cat insoluble Copyright © 2010 Pearson Education, Inc. Chapter Six 6  Agcl and NH Cl are A Both are insoluble B Agd is Soluble NHyd is insoluble C Agd is insoluble NHA is soluble D Both are soluble which of the following in insoluble A Cao B Ca OH C Caso D Nacl  5.5 Acids, Bases, and Neutralization Reactions ► When acids and bases are mixed together in correct proportion acidic and basic properties disappear. ► A neutralization reaction produces water and a salt. HA(aq) + MOH(aq) H2O(l) + MA(aq) acid + base water + salt ► The reaction of hydrochloric acid with potassium hydroxide to produce potassium chloride is an example: ► HCl(aq) + KOH(aq) H2O(l) + KCl(aq) Copyright © 2010 Pearson Education, Inc. Chapter Six 7  5.6 Redox Reactions ► Oxidation– reduction (redox) reaction: A reaction in which electrons transfer from one atom to another. ISH ► Oxidation: Loss of one or more electrons by an atom. Jis 21 ► Reduction: Gain of one or more electrons by an atom. lose é Gaine Copyright © 2010 Pearson Education, Inc. Chapter Six 8 ► Oxidation and reduction always occur together. ► A substance that is oxidized gives up an electron, causes reduction, and is called a reducing agent. ► A substance that is reduced gains an electron, causes oxidation, and is called an oxidizing agent. ► The charge on the reducing agent increases during the reaction, and the charge on the oxidizing agent decreases. Copyright © 2010 Pearson Education, Inc. Chapter Six 9 Reducing agent: ► Loses one or more electrons ► Causes reduction A is making reduction happenbygivinge to B so itscalled ► Undergoes oxidation agent reducing ► Becomes more positive (or less negative) Oxidizing agent: ► Gains one or more electrons agent IE IfatIE afrom ► Causes oxidation ► Undergoes reduction ► Becomes more negative (or less positive) Copyright © 2010 Pearson Education, Inc. Chapter Six 10  5.7 Recognizing Redox Reactions ► One can determine whether atoms are oxidized or reduced in a reaction by keeping track of changes in electron sharing by the atoms. Each atom in a substance is assigned a value called an oxidation number or oxidation state. ► The oxidation number indicates whether the atom is neutral, electron rich, or electron poor. ► By comparing the oxidation state of an atom before and after reaction, we can tell whether the atom has gained or lost electrons. Copyright © 2010 Pearson Education, Inc. Chapter Six 11  ► Rules for assigning oxidation numbers: ► An atom in its elemental state has an oxidation number of zero. ► A monatomic ion has an oxidation number equal to its charge. Copyright © 2010 Pearson Education, Inc. Chapter Six 12 ► In a molecular compound, an atom usually has the same oxidation number it would have if it were a monatomic ion. ► Examples: H often has an oxidation number of +1, oxygen often has an oxidation number of -2, halogens often have an oxidation number of -1. Copyright © 2010 Pearson Education, Inc. Chapter Six 13 ► For compounds with more than one nonmetal element, such as SO2, NO, and CO2, the more electronegative element—oxygen in these examples—has its preferred negative oxidation number. ► The less electronegative element is assigned a positive oxidation number so that the sum of the oxidation numbers in a neutral compound is 0. Copyright © 2010 Pearson Education, Inc. Chapter Six 14 what is the oxidation number of each element in VOC's A 5 2 1 B 4 1 2 C 5 1 2 D 5 2 1 What is reduced and what is the reducing agent Fet Cad cut Fed A Cl Ca B Cu Fe C Fe Cla D Fe Feelz what is the oxidation number of Sulfur in caso A O B 2 C 4 D 6 What is the reducing agent in the following reaction Cut 2Agt Cut 2Ag A Ag B Agt C Cu D Cutz what is the oxidation number of X 0 and s in XOSE A 5 2 2 B 5 2 2 C 5 2 2 D 5 2 2 What is the reducing agent in the following reaction Cut 4Ht 50 cut 2H20 so A Ca B H2O C Cut 2 D So  5.8 Net Ionic Equations ► Ionic equation: An equation in which ions are explicitly shown. ► Spectator ion: An ion that appears unchanged on both sides of a reaction arrow. ► Net ionic equation: An equation that does not include spectator ions. Copyright © 2010 Pearson Education, Inc. Chapter Six 15 what is the net ionic equation NaCl Agnosia Agalist NANO slag A Nat C1 Nachag B Agt CI Agcles c Natt Cl Agt No Agc est Na NO cags D Agtc Agdes what is the net ionic equation 2AgNOz age 4250 2K NO Agz SOyes cag A 2 Agt 2N 2kt so 2kt 2 No 2Agt soj B 2 Agt so Ag SO yes C 2N0j 2kt 2 KNO lag In the following reaction which is a spectator ion 2AgNOz age 4250 cag 2KNO Agz SO yes A Silver and nitrate B Potassium and Sulfate C Potassium and nitrate D Silver and sulfate  Chapter Summary ► Precipitation reactions are processes in which an insoluble solid called a precipitate is formed. ► In acid–base neutralization reactions an acid reacts with a base to yield water plus a salt. ► Oxidation–reduction (redox) reactions are processes in which one or more electrons are transferred between reaction partners. ► Oxidation is the loss of electrons by an atom, and reduction is the gain of electrons by an atom. ► Oxidation numbers are assigned to provide a measure of whether an atom is neutral, electron-rich, or electron-poor. Copyright © 2010 Pearson Education, Inc. Chapter Six 16