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Organic Chemistry Chapter 20 CLEMSON Copyright 2008 Pearson PrenticeHaIl Inc U N I V E R S I T Y Classi cation Scheme for Matter Molecular Compounds Pu re Substances Organic Inorganic Compounds Compounds From Chapter 3 CH 101 Organic Chemistry Organic chemistry is the study of the structure properties composition reactions and preparation of compounds consisting primarily of carbon and hydrogen I May also contain nitrogen oxygen a halogens as well as phosphorus silicon or sulfur I C0 C02 carbonates and carbides are inorganic Organic compounds exhibit a variety of structures an complexities El Organic chemicals touch all aspects of our lives and form the basis of earthly life processes Organic Chemistry Learning Objectives Identify families of organic compounds I Alkanesakenes alkynes acohos ethers amines carboxyllc aCIds and aromatics Isomers Interpret various structural representations of organic molecules Predict physical properties of simple organic compounds based on structure polarity and intermolecular forces I Water solubility boiling point freezing point vapor pressure etc El Nomenclature Be able to name simple alkanes alkenes alkynes and alcohols Carbon Bonding El Carbon compounds generally are covalent I Molecular compounds I Gas amp Liquids I High molecular mass compounds may be solids I Varying solubilities I Polarity depends on family El C C bonds are unreactive stable I Compounds involving chains of carbon atoms can readily form Carbon Bonding El Carbon forms covalent bonds I Electron configuration ls2 2522p2 4 valence electrons El C is most stable when it has 4 single covalent bonds but readily forms double and triple bonds I CC and CEC are more reactive than C C I C with 4 single bonds is tetrahedral sp3 hybridization i H I H H Methagg m Carbon Bonding El Carbon forms covalent bonds El C is most stable when it has 4 single covalent bonds but readily forms double and triple bonds I CC and CEC are more reactive than C C I C with 4 single bonds is tetrahedral I C with 2 single bonds and 1 double bond is trigonal planar sp2 hybridization Carbon Bonding El Carbon forms covalent bonds El C is most stable when it has 4 single covalent bonds but readily forms double and triple bonds I CC and CEC are more reactive than C C I C with 4 single bonds is tetrahedral I C with 2 single bonds and 1 double bond is trigonal planar I C with 1 triple bond and 1 single bond is linear sp Ethyne Copyright 200 Pearson Prenllce Halli Inc Hydrocarbons El Hydrocarbons contain only C and H I aliphatic or aromatic El Insoluble in water I No polar bonds to attract water molecules Aliphatic hydrocarbons I saturated or unsaturated aliphatics I saturated alkanes unsaturated alkenes or alkynes I may be chains or rings I chains may be straight or branched Aromatic hydrocarbons I contain benzene ring structure Alkanes I A hydrocarbon compound in which all carbons have single bonds is called an alkane El These are saturated hydrocarbons as they contain the maximum number of atoms that can bond to a carbon atom l Each carbon is bonded to four other atoms El General formula CnH2n2 where n 1 2 3 El Each carbon has tetrahedral geometry l Each carbon has sp3 hybridization Alkanes Carbon Hybridization El sp3 hybridization El four hybrid orbitals I four single bonds to other atoms Tetrahedral geometry 7 3 El Bond angle 10950 5p hybridized methane ethane propane Alkenes I A carbon hydrogen compound contain at least one carbon carbon double bond is called an alkene El These are unsaturated hydrocarbons as they do not contain the maximum number of atoms that can bond to a carbon atom I Carbons involved in a double bond are bonded to three other atoms El General formula CnH2n El Carbons that are part of the double bond have trigonal geometry Alkenes Carbon Hybridization El sp2 hybridization three hybrid orbitals and one p orbital I two single bonds and one 2 ethene double bond 5pquot hybridized Trigonal planar geometry j El Bond angle 120 0 TV propene U Alkynes I A carbon hydrogen compound contain at least one carbon carbon triple bond is called an alkyne El These are unsaturated hydrocarbons as they do not contain the maximum number of atoms that can bond to a carbon atom I Carbons involved in a triple bond are bonded to two other atoms El General formula CnH2n2 El Carbons that are part of the triple bond have linear geometry Alkynes Carbon Hybridization El sp hybridization two hybrid orbitals and Jz a two p orbitals ehtyne l two double bonds sphybridized or I one triple bond and one single bond Linear geometry El Bond angle 180 O propyne Representations of Hydrocarbons El Chemical Formula tells you what kinds of atoms are in the molecule but doesn t tell you how the atoms are connected 539 C4H10 Representations of Hydrocarbons El Structural Formula shows I number and kinds of atoms I connectivity how the atoms are bonded together I structure in two dimensions only H H H H H HH CJHH H lj lj lj H i i i i I i I C4H10 Representations of Hydrocarbons El Condensed Structural Formula may or may not show bonds l Omits bonds that are understood I May be difficult to interpret CH3 CH3CH2CH2CH3 EH3 H3 CH3 CH CH 3 CH3CHCH3 CH3CHCH3CH3 Representations of Hydrocarbons El Carbon skeleton formula line structure I Each angle and beginning and end represent a C atom I H omitted on C I included on functional groups I Multiple bonds indicated I double line is double bond triple line is triple bond CH3 w I CH3 JH2 N k 5 Representations of Hydrocarbons El Ball and Stick model shows I number and kinds of atoms I connectivity I three dimensional structure quot vV N W 9U Uh CH3 CH3CH2CH2CH3 CH3CHCH3 Representations of Hydrocarbons El Space filling model shows I number and kinds of atoms I connectivity I three dimensional structure CH3 CH3CH2CH2CH3 CH3CHCH3 Representations of Hydrocarbons El Alkenes and Alkynes IIIHH Propene H CC C H CH2CH CH3 A H 1 o J a Propyne H CEC lj H CHEC CHS 5 9 3 4 0 Representations of Hydrocarbons 539 C4H10 El Linear and branched structures possible ibrarytedankarak12tr accessed 9706 Structures of Organic Compounds Isomers Compounds that have the same formula but a different Q bonding arrangement 9 o o of their constituent 0 atoms Isomers El Which would you predict to have the higher boiling point A C4H10 B Isobutane C4H10 C They should have the same boiling point Structures of Organic Compounds El Isomers Compounds that have the same formula but a different bonding arrangement of their constituent atoms l Constitutional isomers different connectivities I Different compounds Physical properties differ Chemical properties differ Different 3D structures 31 ix CH32CHCH3 CH3CH2CHZCH3 nbutane 2methylpropane 0601 relative density liquid 0551 05 boiling point 0C 117 1383 melting point 0C 1596 39 9706 For an Isomers El Rotation about a single bond is not isomerism CH3 CH2 CH2 CH3 CH3 CH2 EH2 Same molecule Copyright 2008 Pearson Prentice Hall Inc Isomers of Hexane 36H14 start by connchng the carbons in a line determine the C skeleton of the other isomers H H HIHTH H HI nYH C HICICICIH H H c H HIJTH H HI nYH 4 H TH thle HnTH H 1 Hl VH H H H HLhTH C6 HLJTH a H IH H H C HINWIH HIJTH HIrH n Icl I X HICIH H chlc m arclH C I H HIJTGJTH H H 4TH H H HI H H f fl 0 h H S C r w a H C h n m t e o n b S O I H L C Isomers of Hexane 361 114 convert each to a carbon skeleton formula each bend and the ends represent C atoms l H H H H H H H H H H H H H i7tflt f H H c c H H H H H H H H H H I H H IZ H H I H HCH H H H H H gig H H H C C H H H H H H H H H Isomers of Pentane 5le El moon Draw all of the constitutional isomers of C5H12 How many did you draw 1 U39ILUJN Isomers of Pentane 5le El Constitutional isomers of C5H12 Pentane T T T T T T T T T H T T TT T H H T C T T H H H H H H H H H H H npentane 2methylbutane bp364 c bp279 c H HH c HH HT T C H HH HH H 2 2dimethylpropane bp95 c neonchemuidahoedu accessed 9706 Alkene Isomers El Double bonds are rigid and do not allow rotation This creates geometric isomers El Geometric isomers have the same chemical formula same atom connectivities but a different structural arrangement El The two main isomers are l cis meaning on the same side I trans meaning on opposing side Alkene Isomers Cis Z butene ch CHq bp 337 C densnty 0616 gmL C C at 25 C H H cisZButene methyl groups on d U the same side J Top view Side View trans Z butene b p 08 C HSC H density 0599 gmL at 2 5 0c C C H CH3 transZButene methyl groups on 39 U opposite sides Top View Side View Alkene Isomers El Linear alkanes do not have cistrans isomers l Atoms can freely rotate around a single bond 391 U L w39 Alkene Isomers cistrans isomerism occurs because the electronic structure of the carbon carbon double bond makes rotation energetically unfavorable Rotate 90 around double bond 24D kJmol Pi bond p orbital overlap Broken bond no p orbital overlap Alkene Isomers El cisZpentene El transZpentene El 2pentene I mixture of isomers Cycloalkanes El Saturated hydrocarbon compounds joined in rings El General formula CnHZn l Constitutional isomers of alkenes El Each carbon has tetrahedral geometry Cyclobutane Cyclopentane Cyclohexane Cyclopropane 391quot Cycloalkanes El Cyclic structures are simplified by using polygons and lines At every line junction it is understood that a carbon and the correct number of hydrogen atoms eXist This threeway intersection is a CH group CH3 This intersection is a CH2 group Methylcyclohexane Aromatic Hydrocarbons The base unit for all aromatic hydrocarbons is the benzene ring Its structure was proposed by Kekul in 1865 0 2 C OH cxg o CH3 HO Benzene Aspirin Estradiol Benzene Flat symmetrical cyclic molecule I Ring carbon hybridization is sp2 Three double bonds or I Resonance structures I Delocalized electrons Aromatic Hydrocarbons El The benzenes may have other atoms attached to it replacing one or more of he hydrogen atoms CH3 CH3 CH2 CI H C H2 CH3 ethylbenzene Chlorobenzene styrene 1 4dimethylbenzene Aromatic Hydrocarbons El Polycyclic Aromatic Hydrocarbons l contain multiple benzene rings fused together fusing sharing a common bond Families of Organic Molecules Hydrocarbons Alkanes single bonded C Alkenes contains a double bond Alkynes contains a triple bond Aromatics contains a benzene ring I Functionalized Hydrocarbons have functional groups substituted for one or more hydrogen atoms I Contain nitrogen oxygen a halogens as well as phosphorus silicon or sulfur l A functional group is a group of atoms that show a characteristic influence on the properties of the molecule Generally the reactions that a compound will perform are determined by what functional groups it contains Hydrocarbons which contain the same functional group are members of the same family Families of Organic Molecules El Functional Group Families I Alcohols I Carboxylic Acids I Ethers I Amines I Aldehydes I Ketones I Esters I Others Organic Chemistry course Families of Organic Molecules El Since the kind of hydrocarbon chain is irrelevant to the reactions it may be indicated by the general symbol R CH3 OH lt R group functional group El ROH I CH3CHZOH Families of Organic Molecules TABLE 2010 Some Common Functional Groups Condensed General General Family Formula Formula Example Name Alcohols R OH ROII CH3CHZOH Ethanol ethyl alcohol Elhers R O R ROR CH 3OCHJ Dinmthyl other l l Aldehydes R H RCHO CI Ig C I39I Ethanal acetaldehyde l l Kelones R C R RCOR CH3 C CH5 Propanone acetone l n Tarbnxylic R C OH RCOOH CH3 C OH Ethanoic acid ad 5 acetic acid 0 ll Esters R C OR RCOOR CH3 C OCH3 Methyl acetate 1391 111 Amines R N R R3N CH3CH2 N H Emylamme 1 1 139 mem r r and mm mp fwn Rgroups my u Alcohols El The hydroxyl functional group OH replaces a hydrogen H in the hydrocarbon l Hydroxyl group is covalently bonded to carbon Not the hydroxide ion OH Ethanol 1 Butanol Comma Alcohols El 0090 What is the dominant type of intermolecular attractive force for alcohols London Dispersion Forces Dipole dipole Interactions CH3 CH2 OH CoDYrigm 2005 Pearson Pfenllce Hall in Hydrogen Bonding Iondipole Interactions Alcohols El Ethane C2H6 CH3CH3 I 300 gmol bp 89 0C El Methanol CH4O CH3OH I 320 gmol bp 65 0c Functional Groups Alcohols El Primary Alcohols have their OH bonded to a terminal carbon that is bonded to one carbon 39 J and two hydrogens El Secondary alcohols have their OH bonded to a carbon that is bonded to two other carbons and one hydrogen Ethers El Contain the R O R linkage where R and R are a hydrocarbon group I R and R may be the same or different hydrocarbon chains CH3 O CH3 CH3 O CH2 CH3 Dimethyl ether Ethyl methyl ether w CH3 CHz O CH2 CH3 MTBE methyltert butylether Die yle he I Copyrlghl 200a Pearson Prentlce Hali Inc Ethers El 0090 What is the dominant type of intermolecular attractive force for ethers London Dispersion Forces Dipoledipole Interactions CH3CHZOCH2CH3 Diethyl ether Hydrogen Bonding Iondipole Interactions Ethers Propane I C3H8 CH3CH2CH3 I 441 gmol I bp 42 C El Dimethylether I C2H6O CH3OCH3 I 461 gmol I bp 23 C El Ethanol C2H6O CH3CHZOH I 461 gmol I bp278 C Amines El Amines are organic derivatives of ammonia NH3 One or more H atoms are replaced by a hydrocarbon chain H3C Methylamine NNdimethylamine NNNtrimethylamine 5 Functional Groups Amines El Amines are bases like ammonia I NH3 H20 gt NH4 OH I H20 gt OH I Amines are easily protonated neutralized in acid solution to form soluble amine salts Amines El 0090 What is the dominant type of intermolecular attractive force for amines London Dispersion Forces Dipole dipole Interactions Hydrogen Bonding Iondipole Interactions CH3 CH2 ITI H H Ethylamlne Copyrighl 2005 Pearson Prentice Hair Inc Amines Propane I C3H8 CH3CH2CH3 I 441 gmol I bp 42 C Ethylamine I C2H7N CH3CH2NH2 I 451 gmol I bp 17 C El Ethanol C2H6O CH3CHZOH I 461 gmol I bp278 C Functional Group Carbonyl El Carbonyl group functional group composed of a carbon atom doublebonded to an oxygen atom CO El Several organic families are based on the carbonyl functional group I R H or carbon chain I X H carbon chain or other atom Functional Group Carbonyl El Carbonyl Functional Group Families carboxylic acids aldehydes ketones esters amides 05 05 05 05 l l l H a c C5H C6C C50 C o C5N f I f 5 f 5 f L Aldehyde Ketone Carboxylic acid Ester Arnde V Less polar More polar Carboxylic Acids El The carboxylic acid functional group COOH replaces a hydrogen H in the hydrocarbon o I Also written as C02H or l Contains a carbonyl carbon 39 w 0 ii CH3 C OH CH3 CH2 CH2 C OH Ethanoic acid or acetic acid Butanoic acid Carboxylic Acids El Carboxylic acids dissociate in water as weak acids to give the carboxylate anion and the hydronium ion CH3C02H H20 gt CH3c02 H3O O 0 CH3C OH CH3C O Carboxylic Acids El What is the dominant type of intermolecular attractive force for carboxylic acids I London Dispersion Forces H CH3 C OH Ethanomacidoraceticaci Hydrogen Bonding 0090 Iondipole Interactions Carboxylic Acids Propane I C3H8 CH3CH2CH3 I 441 gmol I bp 42 C Ethanol I C2H6O CH3CHZOH I 461 gmol I bp 78 0C I Formic acid CH202 HCOOH I 460 gmol I bp101 C Review El Arrange the following compounds by increasing boiling point IIltIVltIIIltI IIltIIIltIVltI IIIltIIltIltIV 0090 IIIltIIltIltIV I II III IV CH3CH2CHZOH CH3OCH2CH3 CH3CH2CH2CH3 CH3COZH Functional Groups Addition of a functional group can change the intermolecular forces Alkanes Alkenes Alkynes Benzene Increasing El Amines R NH2 El Alcohols R OH El Carboxylic acids R COZH Organic Chemistry Review El mpme What would be an appropriate condensed formula for this soap molecule CH3CH28COZNa CH3CH29COZNa CH3CH216COZNa CH3CH217COZNa CH3CH2CH2CH2CH2COZNa Sodium stearate Copyrlgm 2005 Pearson Prentice Halt Inc Chapter 2 Practice Quiz 7 SI 83010 1 Did Aristotle39s theory that matter is composed of four elements last very long 2 Which ofthe following did Lavoisier find a That matter is composed ofatoms b That a pure chemical substance will always contain the same type of toms c That mass is conserved in chemical reactions d That the plum pudding model was incorrect and atoms are mostly space 3 Which ofthe following is not part of Dalton39s atomic theory mallest unit of matter is an atoms b Atoms are composed ofprotons neutrons and electrons c Each element has a unique mass d In a chemical reaction atoms are not changed but rather rearranged 4 What did Millikan39s oil drop experiment determine 5 An atom has 12 protons 12 electrons and 12 neutrons What isotope is the atom a C12 d Mg24 6 What letter represents the atomic number ofa compound 7 Find the average atomic mass ofthe following three isotopes As70 1384 8 You have two isotopes in a population C12 and C14 Find the percent of each isotope considering that the average atomic mass is 1201 amu 9 You have two isotopes in a population Ni59 and Ni56 Findthe percent of each isotope considering that the average atomic mass is 5869 amu 10 How many moles are in 20 grams of fluorine 11How many atoms are in a 82g block ofgold 12How many hydrogen atoms are in 4 m3 of water density ofwater is 1000 k m3 13How many molecules are in one mole oszH30z 14Which has the largest mass 10 mole ofTi or 10 mole ofCo 15 Label the following representations of Helium a He Electrochemistry Chapter 18 CLEMSON UNIVERSITY Batteries El POP What type of reaction is used to generate electrical energy in batteries Acidbase neutralization reaction Precipitation reaction Oxidationreduction reaction I have no clue Electrochemistry El Electrochemistry involves the interconversion of chemical potential energy and electrical energy I Batteries I Manufacturing processes I ie aluminum production I FuelceHs I Corrosion El Oxidation reduction reactions Redox I Electron transfer from one substance to another I Review section 49 I Topics I Balancing oxidationreduction reactions I Types of electrochemical cells I Standard Reduction Potentials and Cell Potentials Electrochemistry El Electrochemical Processes I Batteries I Fuel Cells I Production of Aluminum and Sodium I Corrosion I Combustion El Electrochemical process involve Oxidation Reduction Reactions I An oxidation reduction reaction involves transfer of electrons and changes in oxidation state of elements I Cu2aq Zns gt Cus Zn2aq 2H2g 029 gt 2H20g aka Redox Reaction or electron transfer reaction I Red from reduction I ox from oxidation El Oxidation and reduction are two halves of a whole I Cannot have one without the other Oxidation Reduction Reactions El Oxidation loss of one or more electrons by an element in a substance molecule ion or atom El Reduction gain of one or more electrons by an element in a substance El 2H2g 029 gt 2H20g I Each H atom loses an electron k a J H atoms are oxidized L60 l Each 0 atom gains two electrons O atoms are reduced Oxidation Reduction Reactions n2H2g 029 gt 2H20g l Each H atom an electron H atoms are oxidized Hydrogen is a reducing agent as is causes the reduction of oxygen It supplies electrons for the reduction of oxygen l Each 0 atom two electrons O atoms are reduced Oxygen is an oxidizing agent as it causes the oxidation of hydrogen It takes electrons from hydrogen Oxidation State Convention El Also known as oxidation number El Concept for working with redox reactions El Helps keep track of electrons I Bookkeeping method El Not an ionic charge I Can be for metals El Assigned using rules Rules for Assigning Oxidation States El Rules are in order of priority I Rules higher on list have priority Free elements have an oxidation state of 0 zero 2 Monatomic ions have an oxidation state equal to their charge 3 The sum of oxidation states is O for a neutral compound or equal to the net charge for a polyatomic ion 4 In compounds metals have positive oxidation states i Gp 1A metals always have 1 oxidation state ii Gp 2A metals always have 2 oxidation state Rules for Assigning Oxidation States 5 A nonmetal atom in a formula usually has the same oxidation state it would if it were a monatomic ion i The oxidation state of fluorine is 1 ii The oxidation state of hydrogen is 1 0 Except when bonded to a metal iii The oxidation state of oxygen is 2 i Except peroxides ie H202 iv The oxidation state of a halogen Gp 7A is 1 Expect possibly when bonded to oxygen or another halogen v The oxidation state of Gp 6A is 2 vi The oxidation state of Gp 5A is 3 Oxidation Reduction Reactions El Which element is being oxidized in the following reaction 3HZS 2NO3 2H gt 35 2N0 4HZO mpnpw H S N O I don t know Oxidation Reduction Reactions El Which element is being oxidized in the following reaction Mno2 4HBr gt MnBr2 Br2 ZHZO A Mn B O C H D Br E I don t know Balancing Redox Reactions El Inspection approach often will not work El Two methods I Half reaction Method Preferred to be discussed I Oxidation Number Method Will not be discussed Balancing Redox Reactions El Step 1 Write the unbalanced net ionic equann El A galvanic cell is based on the reaction of iron metal and aqueous potassium permanganate to form aqueous iron II and aqueous Mn II MnO4 aq Fes gt Mn2aq Fe2aq Balancing Redox Reactions El Step 2 Decide which atoms are oxidized and which are reduced Write unbalanced half reactions MnO4 aq Fes gt Mn2aq Fe2aq El Reduced atom Mn 7 to Mn 2 I Oxidized atom Fe O to Fe 2 I Half reactions I Reduction MnO4 aq gt Mn2aq I Oxidation Fes gt Fe2aq Balancing Redox Reactions El Step 3 Balance the half reactions except for O and H I Reduction MnO4 aq gt Mn2aq I Oxidation Fes gt Fe2aq Balanced half reactions all elements except 0 and H I Reduction MnO4 aq gt Mn2aq I Oxidation Fes gt Fe2aq Balancing Redox Reactions El Step 4a Balance oxygen by adding water to side with less 0 I Reduction MnO4 aq gt Mn2aq I Oxidation Fes gt Fe2aq El Oxygen balanced I Reduction MnO4 aq gt Mn2aq I Oxidation Fes gt Fe2aq Balancing Redox Reactions El Step 4b Balance hydrogen by adding H to side with less H I Treats reaction as occurring in acidic solution I Reduction MnO4 aq gt Mn2aq 4H20l I Oxidation Fes gt Fe2aq Hydrogen balanced I Reduction MnO4 aq gt Mn2aq 4HZO I Oxidation Fes gt Fe2aq Balancing Redox Reactions El Step 5a Balance each half reaction charge by adding electrons to the side with the greater positive charge I Reduction MnO4 aq 8Haq gt Mn2aq 4HZOI I Oxidation Fes gt Fe2aq El Balance charge by adding electrons I ReducUon MnO4 aq 8Haq I Oxidation Fes gt Fe2aq gt Mn2aq HZO Balancing Redox Reactions El Step 5b Multiply each half reaction by a suitable factor to make the electron count the same in both half reaction I ReducUon MnO4 aq 8Haq 5e gt Mn2aq 4HZO I Oxidation Fes gt Fe2aq 2e El Make electron count the same in both half reactions I ReducUon 2MnO4 aq 16Haq 10e gt 2Mn2aq 8HZOI I Oxidation 5Fes gt 5Fe2aq 10e Balancing Redox Reactions El Step 6 Add halfreactions together and cancel electrons and other species that appear on both sides of the equation 2MnO4 aq 16Haq we gt 2Mn2aq 8H20 5Fes gt 5Fe2aq 10e 2MnO4aq 5Fes 16Haq a 2Mn2aq 5Fe2aq 8H20 6393 Balancing RedOX Reactions El Check I Atom balance I Charge balance 2MnO4 aq 5Fes 16Haq a 2Mn2aq 5Fe2aq 8H20 Balancing RchX Reactions El mposw What is the coefficient for Ca in the balanced equann 3Cas Au3aq gt Ca2aq Aus don t know Balance the Reaction Balancing RchX Reactions El mposw What is the coefficient for Br in the balanced equann Br03 aq N2H4g a ZBr aq N2g don t know Balance the Reaction Electrochemical Cells El Galvanic Cell I a k a Voltaic Cell I Spontaneous AG is negative oxidationreduction chemical reaction generates electric current I Example battery fuel cell corrosion Electrolytic Cell I Electric current drives a nonspontaneous AG is positive oxidationreduction reaction I Example chlorine production aluminum production Galvanic or Voltaic Cell Overall Zns Cu2aq gt Zn2aq Cus Cu2aq 2 e gt Cus Zn5 gt Zn2aq 2 e Oxidation Reduction Reactions Overall Zns Cu2aq gt Zn2aq Cus What material is being oxidized A Zn B Cu2 C Zn2 D Cu E I m not sure Oxidation Reduction Reactions Overall Zns Cu2aq gt Zn2aq Cus How many electrons are exchanged in this oxidation reduction reaction 0 rnpnpvgt 1 2 3 4 Galvanic or Voltaic Cell Overall Ze lost by each Iquot quota Zn atom oxidized r 3 W Zn U 9 L a Zns Cu2aq gt Zn2aq Cus Salt bridge Containing KN03aq 29quot gained by each Cu ion reduced v Cuz quot Glass wool plugs allow ions to pass ZnN03aq CUN032 1 1 Oxidation Reduction i 7 Zn5 gt 2112 Ze Cu2 25 gt Cus Copyright 2008 Pearson Prentice Hall Inc Galvanic or Voltaic Cell El Cathode of Cu metal immersed in solution containing Cu2 ions physically separated from El Anode of Zn metal immersed in Cupper solution containing Zn2ions El Electron transfer takes place through wire generating an electrical current El Salt bridge connects two solutions Galvanic Cell Anode El Anode the electrode where takes place The species at the anode loses electrons Zns gt Zn2aq 2e generated at anode Given a negative sign Solution around anode contains high concentration M of Zn2 Zns gt Zn2aq 2 e anode Galvanic Cell Cathode El Cathode the electrode where takes place I The species at the anode gains electrons Cu2aq 2e gt Cus Electrons at cathode Given a positive sign El Solution around anode Eolgtalns low concentration oi cathode Cu2quotm7 2 e gt Cus Zns gt Zn2aq 2 e Galvanic Cell Salt Bridge El Oxidation occurs at the anode Zns gt Zn2aq 2e Comments A The halfreaction looks good to me 9 Wait cations cannot exist alone C No problem cations are consumed in the reduction halfreaction D Just let me go back to sleep Galvanic Cell Salt Bridge Salt Bridge maintains an Inert gel that is permeated with a solution of inert gap electrolyte salt I Ions do not react with other ions in solution I Ions are not oxidized or reduced by electrodes I Spectator ions Anions flow toward I Balance Zn2 that is generated Cu2nq 2 equot gt Cus Zns gt Zn2uq 2 e El Cations flow toward I Replace Cu2 that is consumed Galvanic Cell Electrodes El The electrode is not always composed of the metal involved in the half reaction of the redox couple of the cell I Fe3aq e gt Fe2aq reactant and product both in solution I Sn4aq 2e gt Sn2aq gaseous reactant or product I 2Haq 2e gt H2g I CI2g 2e gt 2CI aq Galvanic Cell Electrodes El Inert electrode typically Pt or Cgraphite I Facilitates electron transfer I Does not participate in oxidation or reduction rea ctio n I Mass does not change platinum cathode MnO4 aq 5e 8H gt it Mn2aq 4H20 iron anode Fes gt Fe2aq 2e Oxidation Reduction Fem Fel mqu 2 Mnm39inql 52 sH39mq a MHIWMID JHJOHi Galvanic Cell Electrodes El Inert electrode I Facilitates electron transfer I Does not participate in oxidation or reduction reaction I Mass does not change platinum cathode 2Haq 2e gt H2g Standard hydrogen electrode cathode 2 Haq 2 equot gt H2g Galvanic Cell Electrode Summary Anode El Cathode I Where oxidation occurs I Where reduction occurs I e produced I e consumed I Anions from salt bridge I Cations from salt bridge move towards move towards I Negative sign Positive sign I Like anion I Like cation l e move from negative anode through an external circuit to positive cathode Electrode Review El What is the cathode in the galvanic cell below if the cell reaction is as follows Fes Pb2aq gt Fe2aq Pbs Fe Pb2 Fe2 Pb 0090 Electrochemical Cell Notation El Short hand convention for expressing an electrochemical cell El Anode is placed on the left I Electrons flow from anode to cathode D Salt bridge separates the two half cells n Phases separated Zns I Zn2aq Cu2aq Cus Pts H21 atm H 1 M H Fe3 1 M Fe2 1 M Pts anode half cell cathode half cell oxidation half rx reduction half rx electrode anode sol n cathode sol n electrode Electrochemical Cell Notation El Write the shorthand notation for a galvanic cell that uses the reaction Sn2aq Fes gt Fe2aq Sns Sn2aq Sns Fes Fe2aq Sns Sn2aq Fe2aq Fes Fes Fe2aq Sn2aq Sns Fe2aq Fes Sns Sn2aq 0090 Notes Cell Potential El Potential energy of e in anode is greater than PE of e in cathode Difference in potential is driving force for redox reaction potential energy otential p charge difference U39t nis 1V211 u2aq 2 equot gt Cus Zns gt Zn2aq 2 e Cell Potential El Difference in potential is the driving force for the red19X reaction called the electromotive force or em El For a cell cell potential or Ecell I Depends on Identity of reactants and products Concentration of reactants and products Temperature usually assume to be 25 C El At standard conditions E cell Zns Cu2aq 1 M gt Zn2aq 1 M Cus All solutes at 10 M concentration All gases at 10 atm partial pressure Solids and Liquids in pure form Specified temperature usually 25 C Standard Potential of a Cell El The standard potential of any galvanic cell is the sum of the standard half cell potentials for the oxidation and reduction half cells o o o E cell E oxidation E reduction El E0cell is for galvanic cells I reaction AG lt O I E0cell is for electrolytic cells I Nonspontaneous reaction AG gt O Standard Potential of a Cell El The standard cell potential for our example cell is 110 V Zns Zn2 1 M II Cu2 1 M Cus If the oxidation potential for Zns gt Zn2aq 2e is 076 V what is the reduction potential for Cu2aq 2e gt Cus O34 V O76 V 110 V 034 V 186 V mpnpv Standard Reduction Potential El Standard halfcell potentials are always quoted as a reduction process standard reduction potentials E red I Cu2aq 2e gt Cus E0red 034 V Positive sign indicates spontaneous as written El For an oxidation process reaction is I Cus gt Cu2aq 2e E0OX O34 V Standard Reduction Potential u The reference point is called the standard hydrogen electrode SHE and consists of a platinum 5quot quot electrode in contact with H2 gas at 1 atm and aqueous H ions at 1 M Sta nda rd hyd rugen electrode cathode El The standard hydrogen electrode is assigned an 7 c arbitrary value of exactly zmswzmww mamasarmy 000 V 2Haq 1 M 2e gt H2g 1 atm E SHE 00 V andard Reduction Potentials TABLE 11 Sandal Reduction Putnam a 25 quotC Rs uc nn HanReactim Equot V smmger HAquot 3 3quotquot 1 0 mm uudm n U 103114 1mm M how mlummugcm rlw rvhsorm 21mm Mum 4v Mn lo IHZUU Mum tuqi s H39Auq W a Mn nmn 411mm mm 1f Am Pbmm A HM 2c a WWW z morn 0m 1quot 211 m 12077114 Human w 2 mn 7110 131x 7 run 4 46 2mm mom mm 25 4 Mn me 2mmquot lo M 31qu if aglw mgum mm v 4 2m qu vug nun H39rmn r gt vuz39uun v mom Nurrurn a Il39mp Je39 gt mm 2Hll an e 4 an mm mm F gt Agm FMquot 1 4 Fr mm 0113 l39ml 1 a loam mm 390 e a mm W gl v 26 arm u mq lt cum U113 v IIIUIJ lc A run m1 nq 2 4gt inns an 1 mm 6 Av mummy mum u ml e 4v mm quq n o Sn mup z luq If 4amp1ng H wa 50 Im Phl39taq pram 4 5M5 mm cum I39m a Pram a rim Zn 4 mm 20 mm M m 39 AID Mgm Nam um m uup 2u39 a nnm my 390 W Svmnpcr oxidizrugagmx um t 4 ms redurimuguu Copyright 2008 Pearson Prentice Hall Standard Reduction Potentials I The more positive E0 the g r e n d e n r e Standard Reduction Potentials at25i39C reduction halfreaction to be spontaneous I The larger E the better the reactant acts as an oxidizing agent I More easily it is reduced l I F2 is an excellent oxidizing agent Reductinn HalfReaction V Bonnium Flu 2 e H 2 F my 287 Weaker lIOnq 21mm 2 c H 2 H100 173 reducing Mnortmn swam 5 e39 H anmn 4140 151 aim Chm 2g H 201117 131 11 14 Hmm 62 H zc mq 7HOl 133 A a 4 mm 4 1r H 2 H100 121 BrglI H 2 group 109 gmw 1 H Ag um rumi r H Fe m 077 oz 2 Hm ztr H mogul 070 15 Ze H 2 HM 054 oz 2 H3011 4 0 H 4 0mm 110 Cuban 2 C39 H Cu5l 1134 Sn llq 2 e H Snl fnq 1115 2 Hmrq 2 H 1123 D Ph1 uq 20 gt Pbls 4113 N nql T 21 H N115 425 0111111 2 c H cars Ho 40 Fe m7 2c Hgt 1795 0 45 Zn aq 2c H 2115 D7o 2 l 1101 2 e H Hltg ZUH mq 41253 Aanq 3r H A1SJ 7166 Mglwnq zlr H Mgls 7237 WW I oxidizng Na tnq c H Nam H27 m1 mg m Li mq e H Li39 4 1H 1 HI I Li is an extremely poor oxidizing agent Standard Reduction Potentials 11 The more negative E0 the greater the tendency for the reverse halfreaction oxidation to be spontaneous 11 The smaller E the better the product acts as a reducing agent I More easily it is oxidized 1 Li metal is an excellent reducing agent 1 F is a very poor reducing agent YABLE 181 Standard Reduction Potentialsat 25 C 5 Reduction HalfReaction V Nix11131 r Flag 2 c39 H 2 F nql 287 Vcakor mullml Hlogmq 2 H tuq 2 tr H 2 H30 178 reducing W39 MnOfliiq 51 min 59 H imam 1 117100 151 mg 2 039 H 2011le 136 CEO31111 14 Hmun 132 H 2Cr mm 7 11101 133 02m 1 H lmn 4c H 211200 123 13er 2 13 H 2 Brow 109 Ag lnq c H Ag5 080 FL nl 039 H wholly 1177 0113 2 Hmul 25 H HZOZMD 0711 115 2 c H 2 l39m 054 I 0313 2 Hloll 4 1339 H 4 OH lmI 040 0130117 c H curs 031 Sn miq 2 c H Sn 1117 1115 zl qu 29 H H2g 0 1111301171 Ze H w 71113 NF mq 2c H NH 70 26 Cdl hm A 2 c H car 71110 Fawn 25 H m 1 7045 an tnq 2L H Zns 07 2 HIGH 2c H Hep 201mm 4783 Alma 1 e H ANS 1 be weaker Mgr qu 2 1339 H Mgb 7237 1 qu oxidizing Na fmii 0 4gt N l 4739 1111mm agent Irwin r H 111 404 1 111 Standard Reduction Potentials 11 The strongest oxidizing agents are on the left TABLE 181 Standard Reduction Potentials at 25 C reactant side at the top of the table 3333 I S ontaneous consume e ectrons I Example F2g 11 The strongest reducing agents are on the bottom rigbht product side of the ta e I S ontaneously produce e ectrons w I Example Lis 11 An oxidizing agent on left will react with any reducing agents on right below it on the table Eu Reductinn HalfReaction V Flt4 2 tr e 2 F 1117 287 Weake 1130211117 4 211mm 29 Hzlrlgou 178 mduci g quot4 llnO13911q 8 wing Se39 M 0117 4 4 H 01 151 am 013 z e39 C 111 135 Crzo uq 14 H inq 6e 8 2 Cri iim 7 H10 1 33 033 4 11nq 1c a 2112011 123 Erl e gt 2 13mm 109 g 1 6 Agls 080 I m my u FanqJ 077 My 2 Hmun 2a a Hlozonn 171 Us 2 u 2 Hwy 054 0m 2 H1011 46 HJOH 1 1 11411 Culmni 2c 6 015 1131 5111mm 25 a Sn1 I 015 2 Ha1 212 gt 1113 0 whiting 20 gt 1 bs 4113 Nin17 2 gt M 1 7026 Cdlmul H 1 7040 FDZWIq 2 4 1lt lt 7045 an mln 1 s 4L76 2 H300 7 gt HIQQ zowmq 7083 A qu z a Alm 7161 a Mgzmnp a Mgl 7237 MW 3 g Na lnq a Nai 17 hm 391 gum Lmnq 4 H L115 401 111 Standard Potential of a Cell El The standard potential of any galvanic cell is the sum of the standard half cell potentials for the oxidation and reduction half cells E E E El We can use the tabulated standard reduction potentials to calculate Eoce cell oxidation reduction Calculating Cell Potential What is E0cell for the galvanic cell based on the following redox reaction Nis 2Cuaq gt Ni2aq 2Cus Reduction Potentials from Table 181 Cuaq e gt Cus E0 052V Ni2aq 2e gt Nis E0 O23 V Calculating Cell Potential Reduction Cuaq e gt Cus E0red 052 v Oxidation Nis gt Ni2aq 2e EOOX 023 v Overall Nis 2Cuaq gt Ni2aq Cus Eoce V Calculating Cell Potential What is E0reduction for Cu2 2e gt Cu based on the following redox reaction if E0cell 046 V Cus 2Agaq gt Cu2aq 2Ags Reduction Potentials from Table 181 Agaq e gt Ags E0 080 V A 034V D O34V B 0114V E 114V C 006 V Calculating Cell Potential Calculating Cell Potential Again El What is the potential for the reaction that takes place at the cathode if E I 122 V cel Pts Fe2aq Fe3aq 5208216161 504216167 Pts For Fe3aq e gt Fe2aq E0 079 V A 043V C 28OV B 201V D O36V Calculating Cell Potential Cell Potential El Cell potential and free energy are directly proportional I F 96500 Cmole e Faraday constant I n moles of e transferred in cell reaction I Standard conditions same as AG AH A80 I All solutes at 10 M concentration I All gases at 10 atm partial pressure I Solids and Liquids in pure form I Specified temperature usually 25 C I In a spontaneous reaction I AG is negative I E0 is positive Spontaneity of 21 Reaction I The value of E Seu is related to the thermodynamic quantities of AG and K I The value of E Ceu is related to AG by AG nFE I The value of is related to AG by AG RT In K El Combining these gives the relationship between E Cell and K E00611 E111 K HF combining constants E00611 In K E00611 10g at 25 C n Spontaneity of 21 Reaction Calculate the standard free energy change AG in kJ and the equilibrium constant K for the following reactions at 25 C Sns 2Cu2aq D Sn2aq 2Cuaq Sn2aq 2e gt Sns E0 O14 V Cu2aq e gt Cuaq E0 015 V 00257 n AGO I IFE C Eocell In K Spontaneity of 21 Reaction Sns 2Cu2aq D Sn2aq 2Cuaq Sn2aq 2e gt Sns E0 O14 Cu2aq e gt Cuaq E0 015 What is E0cell for this reaction A 001V C 029V B 001V D O29V Spontaneity of 21 Reaction Calculate the standard free energy change AG in kJ at 25 C AG nFE Ceu F 96500 Cmol e Sns 2Cu2aq D Sn2aq 2Cuaq Sn2aq 2e gt Sns E0 014 Cu2aq e gt Cuaq E0 015 E cell 029 A 280 kJ C 560 kJ B 28000 kJ D 56000 kJ Calculation Page Spontaneity of 21 Reaction Calculate the equilibrium constant K at 25 C 00257 Eocell In K 1 1 Sns 2Cu2aq D Sn2aq 2Cuaq Sn2aq 2e gt Sns E0 O14 Cu2aq e gt Cuaq E0 015 Eoce A 80 x 104 C 40 x 1022 B 16 x 10 6 D 63 x 109 Calculation Page Spontaneity of 21 Reaction El For a spontaneous reaction I proceeds in forward direction with reactants in their standard states a AG nFE u AG RT1nK El 2 00592 V n E2611 log K Copyright 2008 Pearson Prentice iall Inc The Nernst Equation El For nonstandard conditions AG AG RTIn Q El and EE an Nernst Equation 00257 00591 nat 25 C EE an 13130 logQ Using the Nemst Equation El What is Ecell for the galvanic cell to the right at 25 C N H Pb2aq 2e gt Pbs E0 013 v A9aq e gt Ags E0 080 v Start Thinking Like an Electrochemist El 0093 Identify the anode and cathode reactions What reaction occurs at the anode Pb2aq 2e gt Pbs Pbs gt Pb2aq 2e Agaq e gt Ags Ags gt Agaq e ell Pb2aq 2e gt Pbs E 013 V A9aq e gt Ags E 080 v 5 Think Like an Electrochemist Pb Pb2 II Identify the anode and s 9 aq 31 93 cathode reactions Electrons move from anode to cathode Anode think oxidation El Cathode think reduction Anode Pbs gt Pb2aq 2e I E 013 V I Cathode Agaq e gt Ags I E 080 V El Eocell Don t take off your electrochemist hat yet I What is Ecell for the PMS 2A9731 gt fb2aQ 2ASKS e gt galvanic cell to the right at 25 C Pb El Eoce V E 39 El But aren t standard conditions 1 M for aqueous species El Maybe Nernst can help El EE R T1nQ nF n E 2 E0 00257 an 11 Don t take Off your electrochemist hat yet 2 E CeH 093 v PMS 2A9 W gt Ifb aq 2Ags e gt E 2 E0 00257 an 11 El So do you expect Ece to be bigger or smaller than E Ce Ecell gt Eocell Since Q gt 1 gt Eli Ecell gt E0cell since Q lt 1 I Ecell lt E0cell since Q gt 1 Ecell lt E cell since Q lt 1 0093 Almost done Pb s 2A9 aq sz aq 2A9 s E0cell 093 v EZEO o0257an 11 Q El What is n A 1 B 2 C 3 D 4 Pb2 Q Ag 2 The rest is just math Pb s 2A9 aq sz aq 2A9 s Eoce V 00257 EE an 11 n 2 and Q 0080 El So what is Ece A 092 V B 094 V C 096 V D 090 V Pb2 Q Ag 2 The Nemst Equation 11 A galvanic cell is set up at 25 C as noted Determine the cell potential As AI3 00010 M II Ni2 050 M Nis mm 131 Standard ReductionPotentials 3125K 00257 EE lt11 gm 1n 111 1511 11 11 E1 Reduction HalfReactlon mm 2 c gt 2 F 1111 287 H302m 1 2 H39lml 1 2039 gt 2 H301 1 7a MnO11q E H 111 2 1r H Mnlmnl 4113011 151 0117 2 E a 2 C1111 1319 1207311117 14 H 11111 m gt EON111 7113001 133 Oglg A 11110117 19quot H101 123 B1311 211 gt 2 Emmy 109 Amuq c H A 5 1150 11 111n c gt 111 q 1177 021 ZH39W le gt 1710111111 11711 111s 22 gt 2111 1151 Oats 214100 40 H4OH 0M 040 113011 2 r H 115 n 11 5114mm 2 1r a 511511111 015 2 1 11u 29 gt Ham 1 1 1131111 1 2y gt 1711 N 111 217 gt Nils Cquq 2 e a calm F1gt1 1q 2 1r gt Fem li lmll Aquot Anls gt 1110 2 01111111 gt 11 a MgG 4 Nab Lil Weaker rcducl 111 agent 111 111111 11111111 1111 111 1 The Nemst Equation El unpugt El A galvanic cell is set up at 250C as noted Determine the cell potential As AI3 00010 M II Ni2 050 M Nis TABLE 1 Standard Reduction Potentials at 25quotC What is Eoce 141 V 191 V 136V 096V 3 Reduction HalfReacrum V ltnlmg F293 2 a 2 F mg 287 Weaker Uvdizma Hlozmq 211mm Zu gt 21491 178 reducing 39 MnOfmq 8 Hqu Se gt Mnlmiq 41130 151 am 013 2 e gt z CHM 135 Crlof lnql 14 H nq 6039 gt 2 Crquotaq 7 H10 133 02g 4 Hnq is gt 21120 121 Bizm 2 c gt 2 Brquotnq 109 Ag iq c gt Agls 08L Fu mi c gt Fclmiq 077 Gig 2 Hmup Ze a Hgngiy 170 ms 29 a 2 HM 054 04g 2 HOl 4 c a 4 OHM 040 Culmiq 2 c gt Cu 034 5nnq 2 c a Snlmiq 015 2 H nq 2 e gt Hg 0 Pblmiq 2n39 Nil laq 25 C HIQQ ZOH UMI a Als Weaker a Mg Slrniigxi oxidizing H N85 min in dgcnt Li39nq lt u H Lils d t39lll The Nemst Equation El 0090 n A galvanic cell is set up at 250C as noted Determine the cell potential As AI3 00010 M II Ni2 050 M Nis What is Ece 144V 136V 146V 143V E 2 E0 00257 an Calculation Page The Nemst Equation 11 A alvanic cell represented by the following no ation has Ecell 1250 V What must be Ag in the cell Zns Zn2 100 M H Ag M Ags mm 131 Standard Reduz un 39Po1entials ai 25 c39 E Reduction HalfReactlon 411 gm ram 29 gt 2 F 1117 287 Wener mm 1m H302u1 4 2 Hmnn 1 20 gt 2HOI 17a reducing W MnO uq E H 111 a kquot H Mnlmnl 411300 151 quot150 0117 2 E a 2 C1111 1319 0207311117 14H 1nq m gt 2Cr 1117 7113001 133 015 A 411mm 19quot H10 123 131211 211 gt 2 Emmy 109 g luql c H A 5 11511 11 me r gt FU lq 1177 020 ZH39W le39 gt 17191111111 11711 111s 22 gt 2111 1151 0313 214100 40 noww 0411 1131qu 2 0 8 Cum 0 21 51141117 2 1r a 5111411111 015 2 Huq 2r gt Ham 1 sz lmn 1 2L gt 17mg Niz mq 20 gt 1 is O 5 7 1311an 2 e a db 0 Fvl luql 2 1r gt FLa E E Q Zan 26 ZnL 2 113011 2 r gt 1110 2 117111117 11 Alum 3 i gt 1 Weaker M f m 2 E a MS 111 111111 midi ling Na39lmll 6 4 Nab 1111111 1111 agenl 1111111 H 11m 151 1 The Nemst Equation 11 A galvanic cell redsresented by the following notation has hat must be Ag in the cell Ece V Zns Zn2 100 M H Ag M Ags TA E 1 Standard Reduction Pot ntials at125 C What is Eoce 0037 V 0037 V 2563 V 1563V unpugt 11 E Reductinn HalfReaction V Fglx 2 u H 2 F m7 287 Weaker 11100111 21110111 2r H 217101 178 reducing M1071 4 8 H Unl Se H Mnlwm 4112011 151 Hm C12 2 e39 H 2 Cl391111 136 Cr2 Hm 14 ll 1111 62 H zcl lmp 7111011 133 733 1 wow 15 H 211300 123 Brim 2 c39 H 2 Br39lnq 1119 Agmzq c H A 5 11151 FL mn c a FC3 1117 077 03g z Hwy 2c39 H 11301011 0711 35 Ze H 211111 054 0M 2 H2011 4 r H 4 OH tuq 11411 Cul uq 2 c H Cu 034 Snqu 2 c H Snlqu 015 2 Hquotnq 2 r gt 1123 0 111511117 2v gt blt Nil uul 29 gt Nisl calm 2 5 H cm a FEM H Zns 2 H100 2 tr Arm 32 Limm e39 l H Hg 20141114 H ANS H M1115 H Nals H 415 Nrumur r r 1 1 div 5 The Nemst Equation El A galvanic cell redsresented by the following notation has Ecell 1250 V hat must be Ag In the cell Zns Zn2 100 M H Ag M Ags What is Ag for this cell 42 x 1010 M 24 x 10 11 M 51 x 10 6 M 20 x 105 M 0090 n E 2 E0 00257 an Calculation Page Batteries El Batteries are an important practical application of galvanic voltaic cells I Direct conversion of stored chemical energy to electrical energy I Dry cell or Leclanch Cell first patented in 1866 I Lead acid battery was first rechargable 1859 El Singlecell batteries consist of one galvanic cell I An alkaline battery is a single cell El Multicell batteries consist of several galvanic cells linked in series to obtain the desired voltage I A 12 V automobile battery consist of six individual cells 2 V each Batteries El Disposable Batteries or Primary Cells l Discard after battery is discharged Reactants consumed in redox reaction Chemical reaction is not easily reversed El Rechargeable Batteries or Secondary Cells I Can be discharged and charged repeatedly Applying an external electric current reverses the chemical reaction 0 The reverse reaction is nonspontaneous Alkaline Battery El Disposable Battery Single galvanic cell I Produces 154 volts I Amperage depends on size AAA AA C D etc I Anode is Zinc oxidation I Zns ZOH aq gt ZnOH2s 2e El Cathode is graphite inert with MnO2 paste reduction I 2Mn02s HZO 2e gt Mn203s ZOH aq Overall Reaction I Zns 2Mn02s HZO gt ZnOH2s Mn203s Alkaline Battery El Liquid components are part of a paste not a solution I Electrolyte is a paste of KOH hence name alkaline cell Cathode reduction reaction 2 Mn02 H20 2 6 gt anoa 2 OH Graphite rod Cathode Mn02 paste KOH paste Electrolyte Zinc can Anode 1 Anode oxidation reaction Zn 2 OHquot gt ZnOH2 2 e L DURACELIl terminal Steel case Graphite rod cathode Zinc anode MnOZ in KOH paste I Absorbent separator terminal b Copyright 2008 Pearson Prentice Hall Inc 6395 Lead Acid Storage Battery El Standard automobile battery I 6 cells each 2 V I Many other applications I Battery electric vehicles I Backup electrical power I Offgrid electric systems Positive plales lead gric 5 lled with PbOZ El Rechargeable Lead Acid Storage Battery Anode is lead Pb oxidation I Pbs HZSO4aq gt PbSO4s 2Haq 2e El Cathode is lead dioxide PbO2 reduction I Pb02s HZSO4aq 2Haq 2e gt PbSO4s 2H20 Overall reaction PbSO4 is a product of both the oxidation and reduction half reactions HZSO4 is a reactant for both half reactions Lead Acid Storage Battery El Lead grids filled with I Spongy lead anode I Lead oxide cathode Terminals El Electrolyte is sulfuric Anodm acid Emigrant spongylead Electrolyte 30 solution of H2804 Cathode Lead grid packed with Pb02 El Lead sulfate adheres to grid for recharging Copyrighl 2008 Pearson Prentice Hall Inc I May have separator plates to prevent shorting Batteries versus Fuel Cells El Both a battery and a fuel cell convert chemical energy directly into electricity I Each can be considered a galvanic cell I Each has an anode and a cathode I An oxidationreduction reaction is crucial for both El A battery s reactants are self contained I When exhausted the battery ceases to produce electricity El A fuel cell s reactants are supplied from an external source I As long as reactants are supplied electricity will be produced Hydrogen Fuel Cell El Uses hydrogen and oxygen to directly produce electricity in a redox reaction El Not a combustion reaction I Hydrogen and oxygen can be combusted to give heat I Electricity can be produced indirectly via the combustion reaction I Electrochemical reaction allows transferred electrons to do work I Energy released as electricity I Byproduct heat also generated Hydrogen Fuel Cell El Oxidation reaction at anode 2H2g gt 4Haq 4e El Reduction reaction at cathode 029 4Haq 4e gt 2H20l El Overall reaction 2H2g 029 gt 2H20 Hydrogen Fuel Cell El Anode and Cathode separated by electrolyte I Not consumed in reaction I Phosphoric acid solution H3PO4aq I Potassium hydroxide solution KOHaq I Proton exchange membrane PEM I Solid polymer electrolyte membrane I Solid acid electrolyte I Overcome some disadvantages of PEM Hydrogen Fuel Cell Cupyright The McGraw Hill Companies Inc Permission requifed for reproduction or display H2 in gt a H2 ows 02 flows through channels I through channels I I Anode I Catalyst i I I H2 out 6 H20 and 02 out Proton exchanqe membrane PEMV Anode 2H2g gt 4Haq 4e Cathode 02g 4Haq 4e gt 2H20 Electrolytic Cells El An electrolytic cell uses electrical energy to drive a nonspontaneous chemical reaction I Also an electrochemical cell I Electric current generated externally to cell I The process in an electrolytic cell is the reverse of that in a galvanic cell I Process often referred to as electrolysis n EC AG K small I Nonspontaneous reaction forced to take place Electrolysis Galvanic Cell Converts chemical energy to electrical energy E gt 0 AG lt O Spontaneous Reaction K gt 1 Electrolytic Cell Converts electrical energy to chemical energy E lt 0 AG gt O K lt 1 Nonspontaneous Reaction Electrochemical Cells El Is the battery in your cell phone a galvanic cell or a electrolytic cell Galvanic cell Electrolytic cell Both 0090 I m not sure Electrochemical Cells El Galvanic cell when using phone I Converts stored chemical energy to electrical energy I Spontaneous reaction El Electrolytic cell when charging phone I Converts electrical energy to R stored chemical energy quotif I Non spontaneous reaction la Practice Problems for Test 2 Chem 101 SI 1 1 U1 Fquot 8 9 For the following compounds draw the Lewis Structure state the electron geometry and molecular shape tell the hybridization of the central atoms state the approximate bond angle and label the sigma and pi bonds a CH4O b SF6 c CN39 d l39lgO e NOF Give the formula for the ionic compound that results from a Reaction of aluminum and sulfur b Reaction ofsodium and iodine c Reaction of magnesium and nitrogen State the electron configuration a V b V2 CI V5 Arrange these by increasing melting point a Na20 b MgO c NaF Which electron configuration has the highest 4th ionization energy a 1s2 2s2 2p6 3s2 3p3 b 1s2 2s2 2p6 3s2 3p4 c 1s2 2s2 2p6 3s2 3p2 d 1s2 2s2 2p6 3s2 3p1 Choose the larger species from each pair a Sr or Sr2 b N or N3 c Ni or Ni2 d S239 or Ca2 Choose the element with the more negative electron affinity from each pair a Mg or S b K or Cs c Si or P d Ga or Br What types of orbitals are used in the bonding of Acetaldehyde CHgCHO Describe the exact method to determine whether a bond is polar nonpolar or ionic Also what is an experimental way to determine if it is ionic 10 What is the formal charge of each atom in PO437 11 Determine the empirical formula of with the following mass compositions a 407 C b 51 H c 542 O
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