Class Note for CHEM 112 at UMass(21)
Class Note for CHEM 112 at UMass(21)
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This 13 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Massachusetts taught by a professor in Fall. Since its upload, it has received 15 views.
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Date Created: 02/06/15
Turn on Camtasia Recording Which is the rate determining step 1 Agt B 2 Agt C 3 Agt E E2 32 B 6 Cgt D 7 Cgt E What is the equation for the overall reaction The Raschig veaction produces hydrazine NZH an industrially impovtaut veducing agent from NH and ocr in basic aqueuus minim A propused mechanism is Step 1 Fast NHaq DCl aq gtNHzClaq 0H aq Slap 2 Slaw NHClaq NHaq 4 N7Haq cmq Step 3 Fast N2H5aq owaq Namaq HZOU A NH2C NH3OCI39 OH39 gt N2H4 2HZO B NH3 ZOCI gt N2H5 HZO OH39 2CI39 C 2NH3 ocr gt N2H4 2HZO Cl39 D NH3OCI39 OH39 gt N2H4 HZO Cl39 E 2NH3 OCI gt N2H4 HZO Cl39 For this proven reaction mechanism what will be the rate equahon Overall NO2 COgt COZ NO Slow No2 NO2gt N03 NO Fast N03 co gt No2 co2 A Rate kNOZCO B Rate kCOZNO 0 Rate kNO22 D Rate kNO2 E Rate kN03CO For this proven reaction mechanism what will be the rate equation Fast Equilibrium NO2C H NO2 Cl Slow N020l Cl a NO2 Cl2 H mate n39lwu2Cl B Rate k39NOzCC C Rate k39NO22C D Rate k39NOzC2 N02 a E Rate k39N02C 2 Chemical Equations Depict the kind of reactants and products and their relative amounts in a reaction 4Als 3 029 gt 2AI2O3s The numbers in the front are called stoichiometr39ic coefficients The letters s g and I are the physical states of compounds Chemical Equa rions Because the same atoms are present in a reaction at the beginning and at the end the amount ofmatter in a system does not change I The Law of The Conservation of MaH39er39 2HgOs gt 2 Hgiq 029 Chemical Equa rions Because ofthe principle ofthe conserva rion of maTTer an equa i39ion mus i be balanced It must have the same number of atoms ofthe same kind on both sides Lavoisier 1788 Balancing EquaTions Als Br2liq gt AIZBr6s Examples of Chemical Equilibria Formation of stalactites and stalagmites C30038 H20 C029 Cazaq 2 HCO339aq 10 235 Ca2aq 2 HC03 aq CaC03s C02g H20 36035 mam azure Equilibrium When a reaction is at the rate of the forward reaction equals the rate of the reverse reaction There is no net observed change in the system We use when a system is at equilibrium 12 Properties of an Equilibrium Equilibrium systems are DYNAMIC in constant motion I REVERSIBLE can be approached from either direction Pinkto blue CoH2060I2 gt CoH2040I2 2 H20 Blue to pink CoH2040I2 2 H20 gt CoH2060I2 13 THE EQUILIBRIUM CONSTANT For any type of chemical equilibrium ofthe type the following is a CONSTANT at a given T K is unitIess Always product over reactant If K is known we can predict concentrations of products or reactants If we measure concentrations we can calculate K 14 Wr39i ting Equilibrium Expressions Solids and pure liquids NEVER appear in equilibrium expressions 38 029 3029 l H2003aQ H200 3 HCO339aq H3O Because the solid does not appreciably change concentration Because water is 55 M15 The Reaction Quotient Q In general ALL reacting chemical systems are characterized by their REACTION QUOTIENT Q os Under Any Reaction Conditions Pl dllil ranteiiua ons C Dln Al lB Reactaiit caircenb39ations Reaction quotient 0 If Q K then system is at equilibrium Reaction Quotient amp Equilibrium Constant 17 Reaction Quotient amp Equilibrium Constant 29 129 2mm At any point in the reaction H 2 canonization of Reactsnts and Product Readants proceeding toward equilibrium m HzJUz Concentration of Reactants and Product HI Reaction Quotient amp Equilibrium Constant Ham l I29 4 ZHHQ gt Equilibrium achieved H1 In the equilibrium region Hz 12 HI2 H22 K equilibrium constant Readants proceeding toward equilibrium NH3 H20 A K NH4 OH39 B K NH4 OH39 What is the equilibrium expression NH3aq H200 NH4aq 0H39aq J NH3 C K NH3 H20 D K NH3 N H40H39 N Hf OH39 20 Determining K 2NOCg2 NOg CI2g Place 200 mol of NOCI is a 100 L flask At equilibrium you find 066 molL of NO Calculate K Solution Set of an ICE table of concentrations NOCI NO Cl2 initial Qhange Equilibrium 21 The Meaning of K 1 Can tell if a reaction is productfavored or reactantfavored F0rN2g 3H2g 32 NH3Q Conc of products is much greaterthan that of reactants at equilibrium The reaction is strongly favored 22 The meaning of K AQCKS AgaQ C39aQ Kc AgCl39 18x105 Cone of products is much less than that of reactants at equilibrium The reaction with small K is strongly favor39ed Agwaq Clam AgCIs is productfavored 23 Product or39 Reac i39an l39 Favored Reactant favored K lt 1 Productfavored K gt 1 24 Butane Isobutone Seven The system isubutane returns to are added equilibrium gt gt U 122 gt K M emtlllbtlum mixture at 5 tsebutane SEven isabutane molecules are added so A net or 2 isobutane molecules in molecules and 2 butane nmieebies the system is no longer at equilibrium changed to butane molecules to once again give an equilibrium mixture where the ratio of isubutane to butane is 5m 2 m 251 25 Product or reactant favored Table 161 Selected Equilibrium Constant Values Equilibrium Constant Reaction K at 25 0 Product or MadamFavored Combination Reunion af Nannierab 55 0201 5029 42 X 105 ZHth 029 lt39 2 Hzota 32 x to Nam 3 HA9 lt 2 NHilg 35 x 108 29 024 Z 2 Wu 17 x 10 at 2300 K Ionization of Weak Adds and Base HC02Haq HZOU 2 HCO au H0aq 13 X toquot formic acid cugcozwaq HEW 2 Hgto aq H0 aq 18 x toquot acetic acid H2C0aq H200 HC03 aq H0 aq 42 X 10 1 carbonic arid NHslau HM NHA39aq OH taq 18 gtlt10quot5 ammonia Dissolution of quotInsolublequot Solids Camus Caz taq CDJZ tai 38 x 109 Agclts Ag aq El aq 18 X 1039W 26
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